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If a class has multiple methods having same name but different in parameters, it is known as Method Overloading. If we have to perform only one operation, having same name of the methods increases the readability of the program. Suppose you have to perform addition of the given numbers but there can be any number of arguments, if you write the method such as a(int,int) for two parameters, and b(int,int,int) for three parameters then it may be difficult for you as well as other programmers to understand the behavior of the method because its name differs. So, we perform method overloading to figure out the program quickly. Advantage of method overloadingMethod overloading increases the readability of the program. Different ways to overload the methodThere are two ways to overload the method in java
In Java, Method Overloading is not possible by changing the return type of the method only.1) Method Overloading: changing no. of argumentsIn this example, we have created two methods, first add() method performs addition of two numbers and second add method performs addition of three numbers. In this example, we are creating static methods so that we don't need to create instance for calling methods. Test it NowOutput: 2) Method Overloading: changing data type of argumentsIn this example, we have created two methods that differs in data type. The first add method receives two integer arguments and second add method receives two double arguments. Test it NowOutput: Q) Why Method Overloading is not possible by changing the return type of method only?In java, method overloading is not possible by changing the return type of the method only because of ambiguity. Let's see how ambiguity may occur: Test it NowOutput: Compile Time Error: method add(int,int) is already defined in class Adder System.out.println(Adder.add(11,11)); //Here, how can java determine which sum() method should be called? Note: Compile Time Error is better than Run Time Error. So, java compiler renders compiler time error if you declare the same method having same parameters.Can we overload java main() method?Yes, by method overloading. You can have any number of main methods in a class by method overloading. But JVM calls main() method which receives string array as arguments only. Let's see the simple example: Test it NowOutput: Method Overloading and Type PromotionOne type is promoted to another implicitly if no matching datatype is found. Let's understand the concept by the figure given below: As displayed in the above diagram, byte can be promoted to short, int, long, float or double. The short datatype can be promoted to int, long, float or double. The char datatype can be promoted to int,long,float or double and so on. Example of Method Overloading with TypePromotionTest it NowExample of Method Overloading with Type Promotion if matching foundIf there are matching type arguments in the method, type promotion is not performed. Test it NowOutput:int arg method invoked Example of Method Overloading with Type Promotion in case of ambiguityIf there are no matching type arguments in the method, and each method promotes similar number of arguments, there will be ambiguity. Test it NowOutput:Compile Time Error One type is not de-promoted implicitly for example double cannot be depromoted to any type implicitly.
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Here are some guidelines for writing consistent, usable APIs for libraries. NamesNaming is an important part of writing readable, maintainable code. The following best practices can help you achieve that goal. DO use terms consistently.Use the same name for the same thing, throughout your code. If a precedent already exists outside your API that users are likely to know, follow that precedent.
The goal is to take advantage of what the user already knows. This includes their knowledge of the problem domain itself, the conventions of the core libraries, and other parts of your own API. By building on top of those, you reduce the amount of new knowledge they have to acquire before they can be productive. AVOID abbreviations.Unless the abbreviation is more common than the unabbreviated term, don’t abbreviate. If you do abbreviate, capitalize it correctly.
PREFER putting the most descriptive noun last.The last word should be the most descriptive of what the thing is. You can prefix it with other words, such as adjectives, to further describe the thing.
CONSIDER making the code read like a sentence.When in doubt about naming, write some code that uses your API, and try to read it like a sentence.
It’s helpful to try out your API and see how it “reads” when used in code, but you can go too far. It’s not helpful to add articles and other parts of speech to force your names to literally read like a grammatically correct sentence.
PREFER a noun phrase for a non-boolean property or variable.The reader’s focus is on what the property is. If the user cares more about how a property is determined, then it should probably be a method with a verb phrase name.
PREFER a non-imperative verb phrase for a boolean property or variable.Boolean names are often used as conditions in control flow, so you want a name that reads well there. Compare:
Good names tend to start with one of a few kinds of verbs:
What separates all these verb phrases from method names is that they are not imperative. A boolean name should never sound like a command to tell the object to do something, because accessing a property doesn’t change the object. (If the property does modify the object in a meaningful way, it should be a method.)
CONSIDER omitting the verb for a named boolean parameter.This refines the previous rule. For named parameters that are boolean, the name is often just as clear without the verb, and the code reads better at the call site.
PREFER the “positive” name for a boolean property or variable.Most boolean names have conceptually “positive” and “negative” forms where the former feels like the fundamental concept and the latter is its negation—”open” and “closed”, “enabled” and “disabled”, etc. Often the latter name literally has a prefix that negates the former: “visible” and “in-visible”, “connected” and “dis-connected”, “zero” and “non-zero”. When choosing which of the two cases that
For some properties, there is no obvious positive form. Is a document that has been flushed to disk “saved” or “un-changed”? Is a document that hasn’t been flushed “un-saved” or “changed”? In ambiguous cases, lean towards the choice that is less likely to be negated by users or has the shorter name. Exception: With some properties, the negative form is what users overwhelmingly need
to use. Choosing the positive case would force them to negate the property with PREFER an imperative verb phrase for a function or method whose main purpose is a side effect.Callable members can return a result to the caller and perform other work or side effects. In an imperative language like Dart, members are often called mainly for their side effect: they may change an object’s internal state, produce some output, or talk to the outside world. Those kinds of members should be named using an imperative verb phrase that clarifies the work the member performs.
This way, an invocation reads like a command to do that work. PREFER a noun phrase or non-imperative verb phrase for a function or method if returning a value is its primary purpose.Other callable members have few side effects but return a useful result to the caller. If the member needs no parameters to do that, it should generally be a getter. But sometimes a logical “property” needs some parameters. For example, This means the member is syntactically a method, but conceptually it is a property, and should be named as such using a phrase that describes what the member returns.
This guideline is deliberately softer than the previous one. Sometimes a method has no side effects but is still simpler to name with a verb phrase like CONSIDER an imperative verb phrase for a function or method if you want to draw attention to the work it performs.When a member produces a result without any side effects, it should usually be a getter or a method with a noun phrase name describing the result it returns. However, sometimes the work required to produce that result is important. It may be prone to runtime failures, or use heavyweight resources like networking or file I/O. In cases like this, where you want the caller to think about the work the member is doing, give the member a verb phrase name that describes that work.
Note, though, that this guideline is softer than the previous two. The work an operation performs is often an implementation detail that isn’t relevant to the caller, and performance and robustness boundaries change over time. Most of the time, name your members based on what they do for the caller, not how they do it. AVOID starting a method name with get.In most cases, the method should be a getter with Even if the member does need to be a method because it takes arguments or otherwise isn’t a good fit for a getter, you should still avoid
PREFER naming a method to___() if it copies the object’s state to a new object.Linter rule: use_to_and_as_if_applicable A conversion method is one that returns a new object containing a copy of almost all of the state of the receiver but usually in some different form or representation. The core
libraries have a convention that these methods are named starting with If you define a conversion method, it’s helpful to follow that convention.
PREFER naming a method as___() if it returns a different representation backed by the original object.Linter rule: use_to_and_as_if_applicable Conversion methods are “snapshots”. The resulting object has its own copy of the original object’s state. There are other conversion-like methods that return views—they provide a new object, but that object refers back to the original. Later changes to the original object are reflected in the view. The core library convention for you to follow is
AVOID describing the parameters in the function’s or method’s name.The user will see the argument at the call site, so it usually doesn’t help readability to also refer to it in the name itself.
However, it can be useful to mention a parameter to disambiguate it from other similarly-named methods that take different types:
DO follow existing mnemonic conventions when naming type parameters.Single letter names aren’t exactly illuminating, but almost all generic types use them. Fortunately, they mostly use them in a consistent, mnemonic way. The conventions are:
If none of the above cases are a good fit, then either another single-letter mnemonic name or a descriptive name is fine:
In practice, the existing conventions cover most type parameters. LibrariesA leading underscore character ( PREFER making declarations private.A public declaration in a library—either top level or in a class—is a signal that other libraries can and should access that member. It is also a commitment on your library’s part to support that and behave properly when it happens. If that’s not what you intend, add the little CONSIDER declaring multiple classes in the same library.Some languages, such as Java, tie the organization of files to the organization of classes—each file may only define a single top level class. Dart does not have that limitation. Libraries are distinct entities separate from classes. It’s perfectly fine for a single library to contain multiple classes, top level variables, and functions if they all logically belong together. Placing multiple classes together in one library can enable some useful patterns. Since privacy in Dart works at the library level, not the class level, this is a way to define “friend” classes like you might in C++. Every class declared in the same library can access each other’s private members, but code outside of that library cannot. Of course, this guideline doesn’t mean you should put all of your classes into a huge monolithic library, just that you are allowed to place more than one class in a single library. Classes and mixinsDart is a “pure” object-oriented language in that all objects are instances of classes. But Dart does not require all code to be defined inside a class—you can define top-level variables, constants, and functions like you can in a procedural or functional language. AVOID defining a one-member abstract class when a simple function will do.Linter rule: one_member_abstracts Unlike Java, Dart
has first-class functions, closures, and a nice light syntax for using them. If all you need is something like a callback, just use a function. If you’re defining a class and it only has a single abstract member with a meaningless name like
AVOID defining a class that contains only static members.Linter rule: avoid_classes_with_only_static_members In Java and C#, every definition must be inside a class, so it’s common to see “classes” that exist only as a place to stuff static members. Other classes are used as namespaces—a way to give a shared prefix to a bunch of members to relate them to each other or avoid a name collision. Dart has top-level functions, variables, and constants, so you don’t need a class just to define something. If what you want is a namespace, a library is a better fit. Libraries support import prefixes and show/hide combinators. Those are powerful tools that let the consumer of your code handle name collisions in the way that works best for them. If a function or variable isn’t logically tied to a class, put it at the top level. If you’re worried about name collisions, give it a more precise name or move it to a separate library that can be imported with a prefix.
In idiomatic Dart, classes define kinds of objects. A type that is never instantiated is a code smell. However, this isn’t a hard rule. With constants and enum-like types, it may be natural to group them in a class.
AVOID extending a class that isn’t intended to be subclassed.If a constructor is changed from a generative
constructor to a factory constructor, any subclass constructor calling that constructor will break. Also, if a class changes which of its own methods it invokes on Both of these mean that a class needs to be deliberate about whether or not it wants to allow subclassing. This can be communicated in a doc comment, or by giving the class an obvious name like DO document if your class supports being extended.This is the corollary to the above rule. If you want to allow subclasses of your class, state that. Suffix the class name with AVOID implementing a class that isn’t intended to be an interface.Implicit interfaces are a powerful tool in Dart to avoid having to repeat the contract of a class when it can be trivially inferred from the signatures of an implementation of that contract. But implementing a class’s interface is a very tight coupling to that class. It means virtually any change to the class whose interface you are implementing will break your implementation. For example, adding a new member to a class is usually a safe, non-breaking change. But if you are implementing that class’s interface, now your class has a static error because it lacks an implementation of that new method. Library maintainers need the ability to evolve existing classes without breaking users. If you treat every class like it exposes an interface that users are free to implement, then changing those classes becomes very difficult. That difficulty in turn means the libraries you rely on are slower to grow and adapt to new needs. To give the authors of the classes you use more leeway, avoid implementing implicit interfaces except for classes that are clearly intended to be implemented. Otherwise, you may introduce a coupling that the author doesn’t intend, and they may break your code without realizing it. DO document if your class supports being used as an interface.If your class can be used as an interface, mention that in the class’s doc comment. DO use mixin to define a mixin type.Linter rule: prefer_mixin Dart originally didn’t have a separate syntax for declaring a class intended to be mixed in to other classes. Instead, any class that met certain restrictions (no non-default constructor, no superclass, etc.) could be used as a mixin. This was confusing because the author of the class might not have intended it to be mixed in. Dart 2.1.0 added a
You might still encounter
older code using AVOID mixing in a type that isn’t intended to be a mixin.Linter rule: prefer_mixin For compatibility, Dart still allows you to mix in classes that aren’t defined using If the class doesn’t have a doc comment or an obvious name like ConstructorsDart constructors are created by declaring a function with the same name as the class and, optionally, an additional identifier. The latter are called named constructors. CONSIDER making your constructor const if the class supports it.If you have a class where all the fields are final, and the constructor does nothing but initialize them, you can make that constructor If you don’t explicitly make it Note, however, that a MembersA member belongs to an object and can be either methods or instance variables. PREFER making fields and top-level variables final.Linter rule: prefer_final_fields State that is not mutable—that does not change over time—is easier for programmers to reason about. Classes and libraries that minimize the amount of mutable state they work with tend to be
easier to maintain. Of course, it is often useful to have mutable data. But, if you don’t need it, your default should be to make fields and top-level variables Sometimes an instance field doesn’t change after it has been initialized, but can’t be initialized until after the instance is constructed. For example, it may need to reference DO use getters for operations that conceptually access properties.Deciding when a member should be a getter versus a method is a subtle but important part of good API design, hence this very long guideline. Some other
language’s cultures shy away from getters. They only use them when the operation is almost exactly like a field—it does a minuscule amount of calculation on state that lives entirely on the object. Anything more complex or heavyweight than that gets Dart is not like that. In Dart, all dotted names are member invocations that may do computation. Fields are special—they’re getters whose implementation is provided by the language. In other words, getters are not “particularly slow fields” in Dart; fields are “particularly fast getters”. Even so, choosing a getter over a method sends an important signal to the caller. The signal, roughly, is that the operation is “field-like”. The operation, at least in principle, could be implemented using a field, as far as the caller knows. That implies:
If all of the above describe your operation, it should be a getter. It seems like few members would survive that gauntlet, but surprisingly many do. Many operations just do some computation on some state and most of those can and should be getters.
DO use setters for operations that conceptually change properties.Linter rule: use_setters_to_change_properties Deciding between a setter versus a method is similar to deciding between a getter versus a method. In both cases, the operation should be “field-like”. For a setter, “field-like” means:
DON’T define a setter without a corresponding getter.Linter rule: avoid_setters_without_getters Users think of getters and
setters as visible properties of an object. A “dropbox” property that can be written to but not seen is confusing and confounds their intuition about how properties work. For example, a setter without a getter means you can use This guideline does not mean you should add a getter just to permit the setter you want to add. Objects shouldn’t generally expose more state than they need to. If you have some piece of an object’s state that can be modified but not exposed in the same way, use a method instead. AVOID using runtime type tests to fake overloading.It’s common for an API to support similar operations on different types of parameters. To emphasize the similarity, some languages support overloading, which lets you define multiple methods that have the same name but different parameter lists. At compile time, the compiler looks at the actual argument types to determine which method to call. Dart doesn’t have overloading. You can define an API that looks like overloading by defining a single method and then using If callers usually know which type they have and which specific operation they want, it’s better to define separate methods with different names to let callers select the right operation. This gives better static type checking and faster performance since it avoids any runtime type tests. However, if users might have an object of an unknown type and want the API to internally use AVOID public late final fields without initializers.Unlike other Unless you do want users to call the setter, it’s better to pick one of the following solutions:
AVOID returning nullable Future, Stream, and collection types.When an API returns a container type, it has two ways to indicate the absence of data: It can return an empty container or it can return To indicate that your API has no data to provide, prefer returning an empty collection, a non-nullable future of a nullable type, or a stream that doesn’t emit any values. Exception: If returning AVOID returning this from methods just to enable a fluent interface.Linter rule: avoid_returning_this Method cascades are a better solution for chaining method calls.
TypesWhen you write down a type in your program, you constrain the kinds of values that flow into different parts of your code. Types can appear in two kinds of places: type annotations on declarations and type arguments to generic invocations. Type annotations are what you normally think of when you think of “static types”. You can type annotate a variable, parameter, field, or return type. In the following
example,
A generic invocation is a collection literal, a call to a generic class’s constructor, or an invocation of a generic method. In the next example,
We stress the “generic invocation” part here, because type arguments can also appear in type annotations:
Here, Type inferenceType annotations are optional in
Dart. If you omit one, Dart tries to infer a type based on the nearby context. Sometimes it doesn’t have enough information to infer a complete type. When that happens, Dart sometimes reports an error, but usually silently fills in any missing parts with The fact that Dart has both type
inference and a
In other words, whether some code is annotated or inferred is orthogonal to whether it is Inference is a powerful tool to spare you the effort of writing and reading types that are obvious or uninteresting. It keeps the reader’s attention focused on the behavior of the code itself. Explicit types are also a key part of robust, maintainable code. They define the static shape of an API and create boundaries to document and enforce what kinds of values are allowed to reach different parts of the program. Of course, inference isn’t magic. Sometimes inference succeeds and selects a type, but it’s not the type you want. The common case is inferring an overly precise type from a variable’s initializer when you intend to assign values of other types to the variable later. In those cases, you have to write the type explicitly. The guidelines here strike the best balance we’ve found between brevity and control, flexibility and safety. There are specific guidelines to cover all the various cases, but the rough summary is:
DO type annotate variables without initializers.Linter rule: prefer_typing_uninitialized_variables The type of a variable—top-level, local, static field, or instance field—can often be inferred from its initializer. However, if there is no initializer, inference fails.
DO type annotate fields and top-level variables if the type isn’t obvious.Linter rule: type_annotate_public_apis Type annotations are important documentation for how a library should be used. They form boundaries between regions of a program to isolate the source of a type error. Consider:
Here, it’s unclear what
In some cases, though, the type is so obvious that writing it is pointless:
“Obvious” isn’t precisely defined, but these are all good candidates:
If you think the initializer expression—whatever it is—is sufficiently clear, then you may omit the annotation. But if you think annotating helps make the code clearer, then add one. When in doubt, add a type annotation. Even when a type is obvious, you may still wish to explicitly annotate. If the inferred type relies on values or declarations from other libraries, you may want to type annotate your declaration so that a change to that other library doesn’t silently change the type of your own API without you realizing. This rule applies to both public and private declarations. Just as type annotations on APIs help users of your code, types on private members help maintainers. DON’T redundantly type annotate initialized local variables.Linter rule: omit_local_variable_types Local variables, especially in modern code where functions tend to be small, have very little scope. Omitting the type focuses the reader’s attention on the more important name of the variable and its initialized value.
Sometimes the inferred type is not the type you want the variable to have. For example, you may intend to assign values of other types later. In that case, annotate the variable with the type you want.
DO annotate return types on function declarations.Dart doesn’t generally infer the return type of a function declaration from its body, unlike some other languages. That means you should write a type annotation for the return type yourself.
Note that this guideline only applies to named function declarations: top-level functions, methods, and local functions. Anonymous function expressions infer a return type from their body. In fact, the syntax doesn’t even allow a return type annotation. DO annotate parameter types on function declarations.A function’s parameter list determines its boundary to the outside world. Annotating parameter types makes that boundary well defined. Note that even though default parameter values look like variable initializers, Dart doesn’t infer an optional parameter’s type from its default value.
Exception: Function expressions and initializing formals have different type annotation conventions, as described in the next two guidelines. DON’T annotate inferred parameter types on function expressions.Linter rule: avoid_types_on_closure_parameters Anonymous functions are almost always immediately passed to a method taking a callback of some type. When a function expression is created in a typed context, Dart tries to infer the function’s parameter types based on the expected type. For example, when you pass a function
expression to
If the language is able to infer the type you want for a parameter in a function expression, then don’t annotate. In rare cases, the surrounding context isn’t precise enough to provide a type for one or more of the function’s parameters. In those cases, you may need to annotate. (If the function isn’t used immediately, it’s usually better to make it a named declaration.) DON’T type annotate initializing formals.Linter rule: type_init_formals If a constructor parameter is using
DO write type arguments on generic invocations that aren’t inferred.Dart is pretty smart about inferring type arguments in generic invocations. It looks at the expected type where the expression occurs and the types of values being passed to the invocation. However, sometimes those aren’t enough to fully determine a type argument. In that case, write the entire type argument list explicitly.
Sometimes the invocation occurs as the initializer to a variable declaration. If the variable is not local, then instead of writing the type argument list on the invocation itself, you may put a type annotation on the declaration:
Annotating the variable also addresses this guideline because now the type arguments are inferred. DON’T write type arguments on generic invocations that are inferred.This is the converse of the previous rule. If an invocation’s type argument list is correctly inferred with the types you want, then omit the types and let Dart do the work for you.
Here, the type annotation on the field provides a surrounding context to infer the type argument of constructor call in the initializer.
Here, the types of the collection and instance can be inferred bottom-up from their elements and arguments. AVOID writing incomplete generic types.The goal of writing a type annotation or type argument is to pin down a complete type. However, if you write the name of a generic type but omit its type arguments, you haven’t fully specified the type. In Java, these are called “raw types”. For example:
Here, Instead, if you’re writing a generic type either in a type annotation or as a type argument inside some invocation, make sure to write a complete type:
DO annotate with dynamic instead of letting inference fail.When inference doesn’t fill in a type, it usually defaults to When
Note that it’s OK to omit the type when Dart successfully infers
Here, Dart infers Exception: Type annotations on unused parameters ( PREFER signatures in function type annotations.The identifier
Exception: Sometimes, you want a type that represents the union of multiple different function types. For example, you may accept a function that takes one parameter or a function that takes two. Since we don’t have union types, there’s no way to precisely type that and you’d normally have to use
DON’T specify a return type for a setter.Linter rule: avoid_return_types_on_setters Setters always return
DON’T use the legacy typedef syntax.Linter rule: prefer_generic_function_type_aliases Dart has two notations for defining a named typedef for a function type. The original syntax looks like:
That syntax has a couple of problems:
The new syntax looks like this:
If you want to include a parameter’s name, you can do that too:
The new syntax can express anything the old syntax could express and more, and lacks the error-prone misfeature where a single identifier is treated as the parameter’s name instead of its type. The same function type syntax after the The old typedef syntax is still supported to avoid breaking existing code, but it’s deprecated. PREFER inline function types over typedefs.Linter rule: avoid_private_typedef_functions In Dart 1, if you wanted to use a function type for a field, variable, or generic type argument, you had to first define a typedef for it. Dart 2 supports a function type syntax that can be used anywhere a type annotation is allowed:
It may still be worth defining a typedef if the function type is particularly long or frequently used. But in most cases, users want to see what the function type actually is right where it’s used, and the function type syntax gives them that clarity. PREFER using function type syntax for parameters.Linter rule: use_function_type_syntax_for_parameters Dart has a special syntax when defining a parameter whose type is a function. Sort of like in C, you surround the parameter’s name with the function’s return type and parameter signature:
Before Dart 2 added function type syntax, this was the only way to give a parameter a function type without defining a typedef. Now that Dart has a general notation for function types, you can use it for function-typed parameters as well:
The new syntax is a little more verbose, but is consistent with other locations where you must use the new syntax. AVOID using dynamic unless you want to disable static checking.Some operations work with any possible object. For example, a The type Otherwise, prefer using
The main exception to this rule is when working with existing APIs that use DO use Future<void> as the return type of asynchronous members that do not produce values.When you have a synchronous function that doesn’t return a value, you use You may see code that uses For asynchronous functions that do not return a useful value and where no callers need to await the asynchronous
work or handle an asynchronous failure, use a return type of AVOID using FutureOr<T> as a return type.If a method accepts a If you return a
The more precise formulation of this guideline is to only use
ParametersIn Dart, optional parameters can be either positional or named, but not both. AVOID positional boolean parameters.Linter rule: avoid_positional_boolean_parameters Unlike other types, booleans are usually used in literal form. Values like numbers are usually wrapped in named constants, but we
typically pass around
Instead, prefer using named arguments, named constructors, or named constants to clarify what the call is doing.
Note that this doesn’t apply to setters, where the name makes it clear what the value represents:
AVOID optional positional parameters if the user may want to omit earlier parameters.Optional positional parameters should have a logical progression such that earlier parameters are passed more often than later ones. Users should almost never need to explicitly pass a “hole” to omit an earlier positional argument to pass later one. You’re better off using named arguments for that.
AVOID mandatory parameters that accept a special “no argument” value.If the user is logically omitting a parameter, prefer letting them actually omit it by making the parameter optional instead of forcing them to pass Omitting the parameter is more terse and helps prevent bugs where a sentinel value like
DO use inclusive start and exclusive end parameters to accept a range.If you are defining a method or function that lets a user select a range of elements or items from some integer-indexed sequence, take a start index, which refers to the first item and a (likely optional) end index which is one greater than the index of the last item. This is consistent with core libraries that do the same thing.
It’s particularly important to be consistent here because these parameters are usually unnamed. If your API takes a length instead of an end point, the difference won’t be visible at all at the call site. EqualityImplementing custom equality behavior for a class can be tricky. Users have deep intuition about how equality works that your objects need to match, and collection types like hash tables have subtle contracts that they expect elements to follow. DO override hashCode if you override ==.Linter rule: hash_and_equals The default hash code implementation provides an identity hash—two objects generally only have the same hash code if they are the exact same object. Likewise, the default behavior for If you are overriding DO make your == operator obey the mathematical rules of equality.An equivalence relation should be:
Users and code that uses AVOID defining custom equality for mutable classes.Linter rule: avoid_equals_and_hash_code_on_mutable_classes When you define Most hash-based collections don’t anticipate that—they assume an object’s hash code will be the same forever and may behave unpredictably if that isn’t true. DON’T make the parameter to == nullable.Linter rule: avoid_null_checks_in_equality_operators The language specifies that
Is it permissible to define two methods in a class that have identical method names and parameter lists but different return value types or different modifiers?It is allowed to have identical method names, as long as the parameter types are sufficintly different. It is not allowed to have overloaded methods where the difference is just based on return types or modifiers.
Can we have two methods in a class with the same name?Two or more methods can have the same name inside the same class if they accept different arguments. This feature is known as method overloading. Method overloading is achieved by either: changing the number of arguments.
Can we have two methods in a class with the same name in Java?For convenience, Java allows you to write more than one method in the same class definition with the same name. For example, you can have two methods in ShoppingCart class named computeCost. Having two or more methods named the same in the same class is called overloading.
What modifier should you use on a class so that a class in the same package can access it?What modifier should you use on a class so that a class in the same package can access it but a class (including a subclass) in a different package cannot access it? > Use the default modifier.
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