Strings in Java

In Java, a String is an object that represents a sequence of characters. Java provides a robust and flexible API for handling strings, allowing for various operations such as concatenation, comparison, and manipulation. In this article, we will go through the Java String concept in detail.

What are Strings in Java?

Strings are the type of objects that can store the character of values and in Java, every character is stored in 16 bits i,e using UTF 16-bit encoding. A string acts the same as an array of characters in Java.

Example:  

String name = "Geeks";

String Example in Java

Below is an example of a String in Java:

// Java Program to demonstrate
// String
public class StringExample {

    // Main Function
    public static void main(String args[])
    {
        String str = new String("example");
        // creating Java string by new keyword
        // this statement create two object i.e
        // first the object is created in heap
        // memory area and second the object is
        // created in String constant pool.

        System.out.println(str);
    }
}

example

Ways of Creating a String

There are two ways to create a string in Java: 

• String Literal
• Using new Keyword

Syntax:  

<String_Type> <string_variable> = "<sequence_of_string>"; 

1. String literal

To make Java more memory efficient (because no new objects are created if it exists already in the string constant pool). 

Example:

String demoString = “GeeksforGeeks”;

2. Using new keyword

• String s = new String(“Welcome”);
• In such a case, JVM will create a new string object in normal (non-pool) heap memory and the literal “Welcome” will be placed in the string constant pool. The variable s will refer to the object in the heap (non-pool)

In the given example only one object will be created. Firstly JVM will not find any string object with the value “Welcome” in the string constant pool, so it will create a new object. After that it will find the string with the value “Welcome” in the pool, it will not create a new object but will return the reference to the same instance.

Example:

String demoString = new String (“GeeksforGeeks”);

Interfaces and Classes in Strings in Java

CharBuffer: This class implements the CharSequence interface. This class is used to allow character buffers to be used in place of CharSequences. An example of such usage is the regular-expression package java.util.regex.

String: It is a sequence of characters. In Java, objects of String are immutable which means a constant and cannot be changed once created.

CharSequence Interface

CharSequence Interface is used for representing the sequence of Characters in Java.
Classes that are implemented using the CharSequence interface are mentioned below and these provides much of functionality like substring, lastoccurence, first occurence, concatenate , toupper, tolower etc.

1. String
2. StringBuffer
3. StringBuilder

1. String

String is an immutable class which means a constant and cannot be changed once created and if wish to change , we need to create an new object and even the functionality it provides like toupper, tolower, etc all these return a new object , its not modify the original object. It is automatically thread safe.

Syntax

String str= "geeks";
           or
String str= new String("geeks")

2. StringBuffer

StringBuffer is a peer class of String, it is mutable in nature and it is thread safe class , we can use it when we have multi threaded environment and shared object of string buffer i.e, used by mutiple thread. As it is thread safe so there is extra overhead, so it is mainly used for multithreaded program.