Java Language Tutorial in Hindi 5 Package, String and String Buffer смотреть онлайн

This tutorial is made for learning about the package with example of Java Programming Language in Hindi.

A Java package is a mechanism for organizing Java classes into namespaces similar to the modules of Modula, providing modular programming in Java. Java packages can be stored in compressed files called JAR files, allowing classes to be downloaded faster as groups rather than individually.

What Is a Package?

A package is a namespace that organizes a set of related classes and interfaces. Conceptually you can think of packages as being similar to different folders on your computer. You might keep HTML pages in one folder, images in another, and scripts or applications in yet another. Because software written in the Java programming language can be composed of hundreds or thousands of individual classes, it makes sense to keep things organized by placing related classes and interfaces into packages.

The Java platform provides an enormous class library (a set of packages) suitable for use in your own applications. This library is known as the "Application Programming Interface", or "API" for short. Its packages represent the tasks most commonly associated with general-purpose programming. For example, a String object contains state and behavior for character strings; a File object allows a programmer to easily create, delete, inspect, compare, or modify a file on the filesystem; a Socket object allows for the creation and use of network sockets; various GUI objects control buttons and checkboxes and anything else related to graphical user interfaces. There are literally thousands of classes to choose from. This allows you, the programmer, to focus on the design of your particular application, rather than the infrastructure required to make it work.

This tutorial is made for learning about the String and its functions with example of Java Programming Language.

The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase. Case mapping is based on the Unicode Standard version specified by the Character class.

STRINGS IN JAVA

Java String Class is immutable, i.e. Strings in java, once created and initialized, cannot be changed on the same reference. A java.lang.String class is final which implies no class and extend it. The java.lang.String class differs from other classes, one difference being that the String objects can be used with the += and + operators for concatenation.

Two useful methods for String objects are equals( ) and substring( ). The equals( ) method is used for testing whether two Strings contain the same value. The substring( ) method is used to obtain a selected portion of a String.

String Methods

int codePointAt(int index):It is similar to the charAt method however it returns the Unicode code point value of specified index rather than the character itself.
void getChars(int srcBegin, int srcEnd, char[] dest, int destBegin): It copies the characters of src array to the dest array. Only the specified range is being copied(srcBegin to srcEnd) to the dest subarray(starting fromdestBegin).
boolean equals(Object obj): Compares the string with the specified string and returns true if both matches else false.
boolean contentEquals(StringBuffer sb): It compares the string to the specified string buffer.
boolean equalsIgnoreCase(String string): It works same as equals method but it doesn’t consider the case while comparing strings. It does a case insensitive comparison.
int compareTo(String string): This method compares the two strings based on the Unicode value of each character in the strings.
int compareToIgnoreCase(String string): Same as CompareTo method however it ignores the case during comparison.
boolean regionMatches(int srcoffset, String dest, int destoffset, int len): It compares the substring of input to the substring of specified string.

substring (starting from the specified offset index) is having the specified prefix or not.
boolean startsWith(String prefix): It tests whether the string is having specified prefix, if yes then it returns true else false.

This tutorial is made for learning about the String and its functions with example of Java Programming Language.

Java StringBuffer class

Java StringBuffer class is used to created mutable (modifiable) string. The StringBuffer class in java is same as String class except it is mutable i.e. it can be changed.

StringBuffer is a mutable sequence of characters. It is like a String but the contents of the StringBuffer can be modified after creation.

StringBuffer Capacity
Every StringBuffer object has a capacity associated with it. The capacity of the StringBuffer is the number of characters it can hold. It increases automatically as more contents added to it.