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What is String?

String is a nothing but a sequence of characters within double quotes. For example - "Hello World" is a String literal, using it we can create a String object, which is an instance of String class.

How a String object is created?

A String object can be constructed in various ways and some are explained below -:

• String  s = "Hello There";

This line of code creates a new String object with a string literal value Hello There and the String object is referred by a reference variable s.




• String s = new String("Hello There");

This line of code creates a String object using the new keyword and initialize it with a value Hello There, by passing the value to the constructor of String class. This object is assigned to a reference variable s.




• String s = new String();  // line 1
  s = "Hello There"; 	  // line 2

In the code above, line 1 creates an empty String object using new keyword and it is referred by reference variable s. In line 2, this String object referred by reference variable s, is initialized to a value Hello There.

All the three ways described above create a String object with value Hello There on the heap portion of memory and assign it to a reference variable, s.





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Note :


String objects can be added by using + operator between them or by calling concat() method of String class.






Creating and initializing String objects.


Here in program below, we have created and initialized four String objects, each in a different way.



//Initializing string in different ways. 


public class String1
{
public static void main(String[] ar)
{
String str1 = new String("New York");    //First String object

String str2 = "New Delhi";		//Second String object

String str3 = new String();		//Third String object.
str3 = "London";

System.out.println("String 1 : "+str1);
System.out.println("String 2 : "+str2);
System.out.println("String 3 : "+str3);

String str4 = str1+str2; //addition of two String objects by + operator
System.out.println("String 4 : "+ str4);

}





Output is :




String 1 : New York
String 2 : New Delhi
String 3 : London
String 4 : New YorkNew Delhi





Program Analysis



• First String object is created by calling the constructor of String class and passing it a String literal New York
• Second String object is simply created by assigning a String literal New Delhi to the reference variable, str2 of String type.
• Third String object is created empty but it is initialized with a String value London in the next line.
• Finally, the fourth String object is created by adding the first two String objects using + operator, which gives a new String value New YorkNew Delhi assigned to the reference variable, str4.






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