Packages

A package in Java is used to group (or) collection of sub packages, classes, interfaces, enum, annotations and it as a folder in a file directory. We use packages to avoid name conflicts, and to write a better maintainable code. We can easily understand using package.

✓Types of Packages

Built In Packages : JDK and JRE provide different packages like java, lang, awt.
User Defined Packages : Programmer can create the own package as per requirement.

✓Built In Package

Package		Description
java.applet	:	Provides the classes necessary to create an applet and the classes an applet uses to communicate with its applet context.
java.awt	:	Contains all of the classes for creating user interfaces and for painting graphics and images.
java.beans	:	Contains classes related to developing beans -- components based on the JavaBeans™ architecture.
java.io	:	Provides for system input and output through data streams, serialization and the file system.
java.lang	:	Provides classes that are fundamental to the design of the Java programming language.
java.math	:	Provides classes for performing arbitrary-precision integer arithmetic (BigInteger) and arbitrary-precision decimal arithmetic (BigDecimal).
java.net	:	Provides the classes for implementing networking applications.
java.nio	:	Defines buffers, which are containers for data, and provides an overview of the other NIO packages.
java.rmi	:	Provides the RMI package.
java.security	:	Provides the classes and interfaces for the security framework.
java.sql	:	Provides the API for accessing and processing data stored in a data source (usually a relational database) using the JavaTM programming language.
java.text	:	Provides classes and interfaces for handling text, dates, numbers, and messages in a manner independent of natural languages.
java.util	:	Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).
javax.crypto	:	Provides the classes and interfaces for cryptographic operations.
javax.net	:	Provides classes for networking applications.
javax.print	:	Provides the principal classes and interfaces for the JavaTM Print Service API.
javax.rmi	:	Contains user APIs for RMI-IIOP.
javax.management	:	Provides the core classes for the Java Management Extensions.
javax.script	:	The scripting API consists of interfaces and classes that define Java TM Scripting Engines and provides a framework for their use in Java applications.
javax.sql	:	Provides the API for server side data source access and processing from the JavaTM programming language.
javax.swing	:	Provides a set of "lightweight" (all-Java language) components that, to the maximum degree possible, work the same on all platforms.
javax.tools	:	Provides interfaces for tools which can be invoked from a program, for example, compilers.
javax.transaction	:	Contains three exceptions thrown by the ORB machinery during unmarshalling.

✓User Defined Package

Programmer (or) Developer can create difference type of Packages. We need to understand that Java uses a File System Directory (FSD) to store them that looks like folders on our computers. These are the packages that are defined by the user. First we create a directory like com.jst then create the JstDemo Class inside the directory with the first statement being the package names.

Example of User Defined Packages : package com.jaladhi.jst; public class JstUserDefined { public static void main(String args [ ] ) { System.out.println("Jaladhi Soft Technology (JST)"); } }	Output : Jaladhi Soft Technology (JST)
Example of Uder Defined Packages : package com.jst.jaladhi; public class UserDefinedPackage { public static void main(String args[]) { System.out.println("Jaladhi Soft Technology (JST)"); } }	Output : Jaladhi Soft Technology (JST)

✓java.util.function Package in Java 8

Interface	Description
BiConsumer	Represents an operation that accepts two input arguments and returns no result.
BiFunction	Represents a function that accepts two arguments and produces a result.
BinaryOperator	Represents an operation upon two operands of the same type, producing a result of the same type as the operands.
BiPredicate	Represents a predicate (boolean-valued function) of two arguments.
BooleanSupplier	Represents a supplier of boolean-valued results.
Consumer	Represents an operation that accepts a single input argument and returns no result.
DoubleBinaryOperator	Represents an operation upon two double-valued operands and producing a double-valued result.
DoubleConsumer	Represents an operation that accepts a single double-valued argument and returns no result.
DoubleFunction	Represents a function that accepts a double-valued argument and produces a result.
DoublePredicate	Represents a predicate (boolean-valued function) of one double-valued argument.
DoubleSupplier	Represents a supplier of double-valued results.
DoubleToIntFunction	Represents a function that accepts a double-valued argument and produces an int-valued result.
DoubleToLongFunction	Represents a function that accepts a double-valued argument and produces a long-valued result.
DoubleUnaryOperator	Represents an operation on a single double-valued operand that produces a double-valued result.
Function	Represents a function that accepts one argument and produces a result.
IntBinaryOperator	Represents an operation upon two int-valued operands and producing an int-valued result.
IntConsumer	Represents an operation that accepts a single int-valued argument and returns no result.
IntFunction	Represents a function that accepts an int-valued argument and produces a result.
IntPredicate	Represents a predicate (boolean-valued function) of one int-valued argument.
IntSupplier	Represents a supplier of int-valued results.
IntToDoubleFunction	Represents a function that accepts an int-valued argument and produces a double-valued result.
IntToLongFunction	Represents a function that accepts an int-valued argument and produces a long-valued result.
IntUnaryOperator	Represents an operation on a single int-valued operand that produces an int-valued result.
LongBinaryOperator	Represents an operation upon two long-valued operands and producing a long-valued result.
LongConsumer	Represents an operation that accepts a single long-valued argument and returns no result.
LongFunction	Represents a function that accepts a long-valued argument and produces a result.
LongPredicate	Represents a predicate (boolean-valued function) of one long-valued argument.
LongSupplier	Represents a supplier of long-valued results.
LongToDoubleFunction	Represents a function that accepts a long-valued argument and produces a double-valued result.
LongToIntFunction	Represents a function that accepts a long-valued argument and produces an int-valued result.
LongUnaryOperator	Represents an operation on a single long-valued operand that produces a long-valued result.
ObjDoubleConsumer	Represents an operation that accepts an object-valued and a double-valued argument, and returns no result.
ObjIntConsumer	Represents an operation that accepts an object-valued and a int-valued argument, and returns no result.
ObjLongConsumer	Represents an operation that accepts an object-valued and a long-valued argument, and returns no result.
Predicate	Represents a predicate (boolean-valued function) of one argument.
Supplier	Represents a supplier of results.
ToDoubleBiFunction	Represents a function that accepts two arguments and produces a double-valued result.
ToDoubleFunction	Represents a function that produces a double-valued result.
ToIntBiFunction	Represents a function that accepts two arguments and produces an int-valued result.
ToIntFunction	Represents a function that produces an int-valued result.
ToLongBiFunction	Represents a function that accepts two arguments and produces a long-valued result.
ToLongFunction	Represents a function that produces a long-valued result.
UnaryOperator	Represents an operation on a single operand that produces a result of the same type as its operand.

✓java.util.stream Package in Java 8

Interface Summary
Interface	Description
BaseStream	Base interface for streams, which are sequences of elements supporting sequential and parallel aggregate operations.
Collector	A mutable reduction operation that accumulates input elements into a mutable result container, optionally transforming the accumulated result into a final representation after all input elements have been processed.
DoubleStream	A sequence of primitive double-valued elements supporting sequential and parallel aggregate operations.
DoubleStream.Builder	A mutable builder for a DoubleStream.
IntStream	A sequence of primitive int-valued elements supporting sequential and parallel aggregate operations.
IntStream.Builder	A mutable builder for an IntStream.
LongStream	A sequence of primitive long-valued elements supporting sequential and parallel aggregate operations.
LongStream.Builder	A mutable builder for a LongStream.
Stream	A sequence of elements supporting sequential and parallel aggregate operations.
Stream.Builder	A mutable builder for a Stream.
Class Summary
Class	Description
Collectors	Implementations of Collector that implement various useful reduction operations, such as accumulating elements into collections, summarizing elements according to various criteria, etc.
StreamSupport	Low-level utility methods for creating and manipulating streams.
Enum Summary
Enum	Description
Collector.Characteristics	Characteristics indicating properties of a Collector, which can be used to optimize reduction implementations.

✓Package Class

The Package Class is available in java.lang package. The Package Class provides methods to get information about the specification and implementation of a package.

Example of Package Class :
package com.jaladhi.jst;
public class PackageInformation {
public static void main(String args[]) {
Package p=Package.getPackage("java.lang");
System.out.println("Package Name : " + p.getName());
System.out.println("Specification Title : " + p.getSpecificationTitle());
System.out.println("Specification Vendor : " + p.getSpecificationVendor());
System.out.println("Specification Version : " + p.getSpecificationVersion());
System.out.println("Implementaion Title : " + p.getImplementationTitle());
System.out.println("Implementation Vendor : " + p.getImplementationVendor());
System.out.println("Implementation Version : " + p.getImplementationVersion());
System.out.println("Is Sealed : " + p.isSealed());
}
}

Output :
Package Name : java.lang
Specification Title: Java Platform API Specification
Specification Vendor: Oracle Corporation
Specification Version: 1.8
Implementaion Title: Java Runtime Environment
Implementation Vendor: OpenLogic-OpenJDK
Implementation Version: 1.8.0-272
Is Sealed : false

Example of Package Class :
package com.jaladhi.jst;
public class PackageInformation {
public static void main(String args[]) {
Package p = Package.getPackage("java.util");
System.out.println("Package Name : " + p.getName());
System.out.println("Specification Title : " + p.getSpecificationTitle());
System.out.println("Specification Vendor : " + p.getSpecificationVendor());
System.out.println("Specification Version : " + p.getSpecificationVersion());
System.out.println("Implementaion Title : " + p.getImplementationTitle());
System.out.println("Implementation Vendor : " + p.getImplementationVendor());
System.out.println("Implementation Version : " + p.getImplementationVersion());
System.out.println("Is Sealed : " + p.isSealed());
}
}

Output :
Package Name : java.util
Specification Title: Java Platform API Specification
Specification Vendor: Oracle Corporation
Specification Version: 1.8
Implementaion Title: Java Runtime Environment
Implementation Vendor: OpenLogic-OpenJDK
Implementation Version: 1.8.0-272
Is Sealed : false

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Packages