Java String Constructors

Introduction

To create an empty String, call the default constructor. For example, 

String s = new String();

To create a String initialized by an array of characters, use the constructor shown here: 

String(char chars[ ])

Here is an example: 

char chars[] = { 'a', 'b', 'c' };  
String s = new String(chars);

This constructor initializes s with the string "abc".

To specify a subrange of a character array as an initializer: 

String(char chars[ ], int startIndex, int numChars)

startIndex specifies the index at which the subrange begins, and numChars specifies the number of characters to use. 

char chars[] = { 'a', 'b', 'c', 'd', 'e', 'f' };  
String s = new String(chars, 2, 3);

This initializes s with the characters cde.

To construct a String object from another String object using this constructor: 

String(String strObj)

Here, strObj is a String object. 

// Construct one String from another.  
public class Main {  
  public static void main(String args[]) {  
    char c[] = {'J', 'a', 'v', 'a'};   
    String s1 = new String(c);  
    String s2 = new String(s1);  
  
    System.out.println(s1);  //from w ww.  j a  v a2s .com
    System.out.println(s2);  
  }  
}

String class has constructors that initialize a string when given a byte array.

Two forms are shown here: 

String(byte chrs[])  
String(byte chrs[], int startIndex, int numChars)

The following program illustrates these constructors: 

// Construct string from subset of char array.  
public class Main {  
  public static void main(String args[]) {  
    byte ascii[] = {65, 66, 67, 68, 69, 70 };  
  
    String s1 = new String(ascii);  
    System.out.println(s1);  //  w w w .j  a  v  a2s .  co m
  
    String s2 = new String(ascii, 2, 3);  
    System.out.println(s2);  
  }  
}



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