Java Strings

String Class

In Java a string is a class rather than a character array. In other words, a character array is different from string in Java.

A string is an object with the set of characters. No null indicator at the end of the string object. A string class provides a set of methods that handles strings.

The following is the set of methods in Strings:

For Example,

public class StringDemo{
     public static void main(String args[]){
          String p=args[0];
          String q=args[1];
          String r = p;
          if(p.equalsIgnoreCase(q))
             System.out.println("Same")
          else
            System.out.println("Different")
         
          if(p==q)
            System.out.println("Same")
          else
            System.out.println("Different")
         if(p==r)
            System.out.println("Same")
          else
            System.out.println("Different")
     }
}

Output:

CSE-A   CSE-A
Same
Different
Same

Note: equals() compares the content of the object where as == compares the object references.

An example of string sort:

import java.util.*;
public class StringSort{
 public static void main(String args[]){
   int n,i,j;
   String k[];
   Scanner sc = new Scanner(System.in);
   System.out.println("Enter Number of strings");
   n=sc.nextInt();
   k=new String[n];
   System.out.println("Enter Names");
   for (i=0;i<n;i++)
    k[i]=sc.next();
   for(i=0;i<n;i++){
    for(j=i+1;j<n;j++){
     if(k[i].compareTo(k[j])>0)
     {
       String temp=k[i];
       k[i]=temp;
       k[j]=k[i];
     }
    }
   }
   System.out.println("After Sorting......");
   for(i=0;i<n;i++)
     System.out.println(k[i]);
  }
}

Output,

Enter Number of strings
5
Enter Names
c cplus java python ruby
After Sorting......
c
cplus
java
python
ruby

Now let us see a program with the string methods to toggle the characters in the given string.

Program to convert the given string into toggle case.

import java.util.*;
public class Toggle{
 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  char ch;
  System.out.println("Enter a String");
  String p = sc.next();
  for(int i=0;i<p.length();i++)
  {
   ch=p.charAt(i);
   if((ch>=65) &&(ch<=90))
    ch=Character.toLowerCase(ch);
   else
    ch=Character.toUpperCase(ch);
   System.out.print(ch);
  }
 }
}

Output, which we can do on the command prompt.

Enter a String
python
PYTHON

Now let us try to print prefixes and suffixes of the string:

import java.util.*;
public class StringsDemo{
 public static void main(String[] args) {
  char ch;
  Scanner sc=new Scanner(System.in);
  
  System.out.println("Enter String");
  String p=sc.next();
  
  System.out.println("Prfixes of the string are");
  for(int i=0;i<p.length();i++)
   System.out.println(p.substring(i));
  System.out.println("Sufixes of the string are");
  for(int i=0;i<p.length();i++)
   System.out.println(p.substring(0,i));
}
}

Output will be,

Enter String
Andhrapradesh
Prfixes of the string are
Andhrapradesh
ndhrapradesh
dhrapradesh
hrapradesh
rapradesh
apradesh
pradesh
radesh
adesh
desh
esh
sh
h
Sufixes of the string are
A
An
And
Andh
Andhr
Andhra
Andhrap
Andhrapr
Andhrapra
Andhraprad
Andhraprade
Andhraprades

Now let us check whether the given string is palindrome or not.

import java.util.*;
public class Palindrome{
 
 public static void main(String[] args) {
  
  char ch;
  Scanner sc=new Scanner(System.in);
  
  System.out.println("Enter String");
  String p=sc.next();
String q = new String(p);
  
  System.out.println("Prfixes of the string are");
  
  StringBuffer sb=new StringBuffer(q);
  sb.reverse();
if(p.equals(sb.toString()))
   System.out.println("Palindrome");
  else
   System.out.println("Not Palindrome");
}
}

Output,

E:\Programs\Java>java Palindrome
Enter String
abcdcba
Prfixes of the string are
Palindrome
E:\Programs\Java>java Palindrome
Enter String
abcdef
Prfixes of the string are
Not Palindrome

String Tokenizer:

It divides or splits a string into token(sub strings) based on the given symbol. The symbol should be mentioned in terms of a string. It is present in java.util package. It consists of three methods:

1. hasMoreTokens()
2. nextToken()
3. countTokens()

Let us see this with an example.

Now let us try to divide a sentence into strings.

import java.util.*;
public class STDemo{
 
 public static void main(String[] args) {
  
  String msg="Today is a holiday";
  StringTokenizer st= new StringTokenizer(msg," ");
  while(st.hasMoreTokens())
   System.out.println(st.nextToken());
}
}

Output will be,

Today
is
a
holiday