Introduction to Computer Science - Java


        String is actually a built-in class. Since it is a class, it has methods. Let us see some of the methods it has.

final int position =2;// create a variable named position whose value can never be changed
String s, s1, s2, s3, s4, s5, s6;
char charArray[]={ 'T','o','r','a','h'};
byte byteArray[]={ (byte)'n', (byte)'e', (byte)'w' };

// Constuctor Methods are methods which are called when the object is created.  
// The name of the Constructor Method will always be the 
// same as the class name.  The Constructor Method will never return
// any value. There can be several Constructor Methods for a class
// as long as they each have different parameter lists.
// Here are several Constructor Methods for String.

s = new String ( "hello" );  // copies hello into s
s1 = new String ( ); // make s1 a blank String
s2 = new String (s); // copies value of s into s2
s3 = new String ( charArray ); // copies value of charArray into s3 (i.e. "Torah")
s4 = new String ( charArray, 1, 3 );// 1 is offset, 3 is number of characters to copy
                                    // copies "ora" into s4 
s5 = new String ( byteArray, 0, 3);// copies the first 3 elements of byteArray into s5
s6 = new String ( byteArray ); // copies all of byteArray into s6
// Here are some other useful methods in class String

s.length(); //returns length of String s, don't for get the (), this is a method.
s.charAt(position); // returns the single character at positiion, i.e. 'l'
s.getChars( 1, 3, charArray, 0 ); /*  the first param. is start of copying position,
       the second param. is the index one past the last letter I want to copy,
       charArray is the destination into which to copy,
       the fourth param. is where in the destination array I should starting copying into.
       This will copy "el" into the beginning of charArray, producing the String "elrah". 

s1.equals("hello");  // returns true if s1 is "hello", 
                     // == will only be true if it is the identical object in memory

s1.equalsIgnoreCase("Hello");  //returns true even if one string is UPPERCASE and the other is lowercase

s1.compareTo(s2);   // returns 0 if s1 equals s2
	            // returns a negative number if object s1 < parameter s2
                    // returns a positive number if object s1  > parameter s2

s1.indexOf( 'e' );
s1.indexOf( 'l',2 );  //start looking at index  2
s1.lastIndexOf( 'l' ); // start at end of string, go backwards

s1.substring( 2 ); // start at index 2 till end
s1.substring( 0,2 ); // start at index 0 till 2

s1.concat (s2); //append s2 to end of s1

static class methods int b = 77; String.valueOf(b); //returns 77 as a string

Some examples using Strings

© Nachum Danzig December 2003-2008