Which of the following keyword is used to define a package in java?
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Which of these keywords is used to define packages in Java? Show
pkg Pkg package Package Next Question Which of these is a mechanism for naming and visibility control of a class and its content? Check Answer More TNPSC Videos This is the java programming questions and answers section on "Java Packages" with the explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand. Java Packages Questions
2. Which of these is a mechanism for naming and visibility control of a class and its content?
Answer & ExplanationAnswer: Option B Explanation: Packages are both naming and visibility control mechanism. We can define a class inside a package which is not accessible by code outside the package. WorkspaceReport Error3. Which of this access specifies can be used for a class so that its members can be accessed by a different class in the same package?
Answer & ExplanationAnswer: Option D Explanation: Either we can use public, protected or we can name the class without any specifier. WorkspaceReport Error4. Which of these access specifiers can be used for a class so that it's members can be accessed by a different class in the different package?
WorkspaceReport ErrorMock Tests & Online QuizzesA snippet of Java code with keywords highlighted in blue and bold font In the Java programming language, a keyword is any one of 67 reserved words[1] that have a predefined meaning in the language. Because of this, programmers cannot use keywords in some contexts, such as names for variables, methods, classes, or as any other identifier.[2] Of these 67 keywords, 16 of them are only contextually reserved, and can sometimes be used as an identifier, unlike standard reserved words. Due to their special functions in the language, most integrated development environments for Java use syntax highlighting to display keywords in a different colour for easy identification. List of JAVA keywords[edit]_Added in Java 9, the underscore has become a keyword and cannot be used as a variable name anymore.[3]abstract
A method with no definition must be declared as abstract and the class containing it must be declared as abstract. Abstract classes cannot be instantiated. Abstract methods must be implemented in the sub classes. The abstract keyword cannot be used with variables or constructors. Note that an abstract class isn't required to have an abstract method at all.assert (added in J2SE
1.4)[4]Assert describes a predicate (a true–false statement) placed in a Java program to indicate that the developer thinks that the predicate is always true at that place. If an assertion evaluates to false at run-time, an assertion failure results, which typically causes execution to abort. Assertions are disabled at runtime by
default, but can be enabled through a command-line option or programmatically through a method on the class loader.booleanDefines a boolean variable for the values "true" or "false" only. By default, the value of boolean primitive type is false. This keyword is also used to declare that a method returns a value of the primitive type boolean.breakUsed to end the execution in the current loop body.byteThe
byte keyword is used to declare a field that can hold an 8-bit signed two's complement integer.[5][6] This keyword is also used to declare that a method returns a value of the
primitive type byte.[7][8]caseA statement in the switch block can be labeled with one or more case or default
labels. The switch statement evaluates its expression, then executes all statements that follow the matching case label; see switch.[9][10]catch
Used in conjunction with a try block and an optional finally block. The statements in the catch block specify what to do if a specific type of exception is thrown by the try block.charDefines a character variable capable of holding any character of the java source file's character set.classA type that defines the implementation of a particular kind of object. A class definition defines
instance and class fields, methods, and inner
classes as well as specifying the interfaces the class implements and the immediate superclass of the class. If the superclass is not explicitly specified, the superclass is implicitly Object. The class keyword can also be used in the form
Class.class to get a Class object without needing an instance of that class. For example, String.class can be used instead of doing new String().getClass().constUnused but reserved.continueUsed to resume program execution at the end of the current loop body. If followed by a label, continue resumes execution at the end of the enclosing labeled loop body.defaultThe
default keyword can optionally be used in a switch statement to label a block of statements to be executed if no case matches the specified value; see
switch.[9][10] Alternatively, the default keyword can also be used
to declare default values in a Java annotation. From Java 8 onwards, the default keyword can be used to allow an interface to provide an implementation of a method.doThe do keyword is used in conjunction with while to create a do-while
loop, which executes a block of statements associated with the loop and then tests a boolean expression associated with the while. If the expression evaluates to true, the block is executed again; this continues until the expression evaluates to
false.[11][12]doubleThe double keyword is used to declare a variable that can hold a 64-bit
double precision IEEE 754 floating-point number.[5][6] This keyword is also used to declare that a method returns a value of the primitive type
double.[7][8]elseThe else keyword is used in conjunction with if to create an
if-else statement, which tests a boolean expression; if the expression evaluates to true, the block of statements associated with the if are evaluated; if it evaluates to false, the block of statements associated with the else are
evaluated.[13][14]enum (added in J2SE
5.0)[4]A Java keyword used to declare an enumerated type. Enumerations extend the base class Enum.extendsUsed in a class declaration to specify the superclass; used in an interface declaration to specify
one or more superinterfaces. Class X extends class Y to add functionality, either by adding fields or methods to class Y, or by overriding methods of class Y. An interface Z extends one or more interfaces by adding methods. Class X is said to be a subclass of class Y; Interface Z is said to be a subinterface of the interfaces it extends.Also used to specify an upper bound on a type parameter in Generics.finalDefine an entity once that cannot be changed nor
derived from later. More specifically: a final class cannot be subclassed, a final method cannot be overridden, and a final variable can occur at most once as a left-hand expression on an executed command. All methods in a final class are implicitly final.finallyUsed to define a block of statements for a block defined previously by the try keyword. The finally block is executed after execution exits the try block and any associated catch clauses
regardless of whether an exception was thrown or caught, or execution left method in the middle of the try or catch blocks using the return keyword.floatThe float keyword is used to declare a variable that can hold a 32-bit single precision IEEE 754 floating-point
number.[5][6] This keyword is also used to declare that a method returns a value of the primitive type
float.[7][8]forThe for keyword is used to create a
for loop, which specifies a variable initialization, a boolean expression, and an incrementation. The variable initialization is performed first, and then the boolean expression is evaluated. If the expression evaluates to true, the block of statements associated with the loop are executed, and then the
incrementation is performed. The boolean expression is then evaluated again; this continues until the expression evaluates to false.[15]As of J2SE 5.0, the for keyword can also be used to create a so-called
"enhanced for loop",[16] which specifies an array or Iterable object; each iteration of the loop executes the associated block of
statements using a different element in the array or Iterable.[15]gotoUnused but reserved.ifThe if keyword is used to create an if statement, which tests a
boolean expression; if the expression evaluates to true, the block of statements associated with the if statement is executed. This keyword can also be used to create an if-else statement; see
else.[13][14]implementsIncluded in a class
declaration to specify one or more interfaces that are implemented by the current class. A class inherits the types and abstract methods declared by the interfaces.importUsed at the beginning of a source file to specify classes or entire
Java packages to be referred to later without including their package names in the reference. Since J2SE 5.0, import statements can import static members of a class.instanceofA binary operator that takes an object reference as its first operand and a class or
interface as its second operand and produces a boolean result. The instanceof operator evaluates to true if and only if the runtime type of the object is assignment compatible with the class or interface.intThe int keyword is used to declare a variable that can hold a 32-bit signed two's complement
integer.[5][6] This keyword is also used to declare that a method returns a value of the primitive type
int.[7][8]interfaceUsed to declare a special type of class that only contains abstract or default methods, constant (static final) fields and
static interfaces. It can later be implemented by classes that declare the interface with the implements keyword. As multiple inheritance is not allowed in Java, interfaces are used to circumvent it. An interface can be defined within another interface.longThe long keyword is used to declare a variable that can hold a 64-bit signed two's
complement integer.[5][6] This keyword is also used to declare that a method returns a value of the primitive type
long.[7][8]nativeUsed in method declarations to specify that the method is not implemented in the same Java source file, but rather in
another language.[8]newUsed to create an instance of a class or array object. Using keyword for this end is not completely necessary (as exemplified by Scala), though it serves two purposes: it enables the existence of different namespace for methods and class names, it defines statically and locally that a fresh object is indeed created, and of what runtime type it is (arguably introducing dependency into the code).packageJava package is a group of similar classes and interfaces. Packages are declared with the package keyword.privateThe private keyword is used in the
declaration of a method, field, or inner class; private members can only be accessed by other members of their own class.[17]protectedThe protected keyword is used in the declaration of a method, field, or inner class; protected members can only be accessed by members of their own class, that class's
subclasses or classes from the same package.[17]publicThe public keyword is used in
the declaration of a class, method, or field; public classes, methods, and fields can be accessed by the members of any class.[17]returnUsed to finish the execution of a method. It can be followed by a value required by the method definition that is returned to the callershortThe short keyword is
used to declare a field that can hold a 16-bit signed two's complement integer.[5][6] This keyword is also used to declare that a method returns a value of the primitive type
short.[7][8]staticUsed to declare a field, method, or inner class as a class field. Classes maintain one copy of class fields regardless
of how many instances exist of that class. static also is used to define a method as a class method. Class methods are bound to the class instead of to a specific instance, and can only operate on class fields. (Classes and interfaces declared as static members of another class or interface are actually top-level classes and are not inner classes.superInheritance
basically used to achieve dynamic binding or run-time polymorphism in java. Used to access members of a class inherited by the class in which it appears. Allows a subclass to access overridden methods and hidden members of its superclass. The super keyword is also used to forward a call from a constructor to a constructor in the superclass.Also used to
specify a lower bound on a type parameter in Generics.switchThe switch keyword is used in conjunction with case and default to create a switch statement, which evaluates a variable, matches its value to a specific case, and executes the block of statements associated with that case. If no case matches the value, the
optional block labelled by default is executed, if included.[9][10]synchronizedUsed in the declaration of a method or code
block to acquire the mutex lock for an object while the current thread executes the code.[8] For static methods, the
object locked is the class's Class. Guarantees that at most one thread at a time operating on the same object executes that code. The mutex lock is automatically released when execution exits the synchronized code. Fields, classes and interfaces cannot be declared as synchronized.thisUsed to represent an instance of the class in which it appears. this can be used to access class members and as a reference to the current instance. The this keyword
is also used to forward a call from one constructor in a class to another constructor in the same class.throwCauses the declared exception instance to be thrown. This causes execution to continue with the first enclosing exception handler declared by the catch keyword to handle an assignment compatible exception type. If no such exception handler is found in the current method, then the method returns and the process is repeated in the calling method. If no
exception handler is found in any method call on the stack, then the exception is passed to the thread's uncaught exception handler.throwsUsed in method declarations to specify which exceptions are not handled within the method but rather passed to the next higher level of the program. All uncaught exceptions in a method that are not instances of RuntimeException must be declared using the throws keyword.transientDeclares that an instance field is
not part of the default serialized form of an object. When an object is serialized, only the values of its non-transient instance fields are included in the default serial representation. When an object is deserialized, transient fields are initialized only to their default value. If the default form is not used, e.g. when a serialPersistentFields table is declared in the class hierarchy, all
transient keywords are ignored.[18][19]tryDefines a block of statements that have exception handling. If an exception is thrown inside the try block, an optional catch
block can handle declared exception types. Also, an optional finally block can be declared that will be executed when execution exits the try block and catch clauses, regardless of whether an exception is thrown or not. A try block must have at least one catch clause or a finally block.voidThe void keyword is used to declare that a method does not return any
value.[7]volatileUsed in field declarations to guarantee visibility of changes to variables across threads. Every read of a volatile variable will be read from main memory, and not from the CPU cache, and that every write to a volatile variable will be written to main memory, and not just to the CPU
cache.[20] Methods, classes and interfaces thus cannot be declared volatile, nor can local variables or parameters.whileThe while keyword is used to create a while loop, which
tests a boolean expression and executes the block of statements associated with the loop if the expression evaluates to true; this continues until the expression evaluates to false. This keyword can also be used to create a do-while loop; see
do.[11][12]Reserved Identifiers[edit]The following identifiers are contextual keywords, and are only restricted in some contexts:
non-sealedUsed to declare that a class or interface which extends a sealed class can be extended by unknown
classes.[21]openopenspermitsThe permits clause specifies the classes that are permitted to extend a sealed class.[21]providesrecord
sealedA sealed class or interface can only be extended or implemented only by classes and interfaces permitted to do so.[21]totransitiveusesvarA special identifier that cannot be used as a type name (since Java
10).[22]withyieldUsed to set a value for a switch expression, when using labelled statement groups (for example, case L:).[23]Reserved words for literal values[edit]trueA boolean literal value.falseA boolean literal value.nullA reference literal value.Unused[edit]constAlthough reserved as a keyword in Java, const is not used and has no
function.[2][24] For defining constants in Java, see the final keyword.gotoAlthough reserved as a keyword in Java, goto is not used and has no
function.[2][24]strictfp (added in J2SE 1.2)[4]Although reserved as a keyword in Java, strictfp is obsolete, and no longer has any function.[25] Previously this keyword was used to restrict the precision and rounding of floating point calculations to ensure
portability.[8]See also[edit]
References[edit]
External links[edit]
Which keyword is used to define package in Java?The package keyword creates a package.
How do you define a package in Java?Syntax: To declare the name of the package to be created. The package statement simply defines in which package the classes defined belong. First Declare The Package Name As The First Statement Of Our Program. Then We Can Include A Class As A Part Of The Package.
Which of these keywords is used to define packages in Java a PKG B PKG C package D package?2. Which of these keywords is used to define packages in Java? Explanation: package keywords is used to define packages in Java.
What is user defined package in Java?Just write a package by following its name. package example1; Step 2: Include class in java package, But remember that class only has one package declaration. Step 3: Now the user-defined package is successfully created, we can import it into other packages and use its functions it.
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