String function in Java ?

Iwe3official
12 Jan, 2023

String function in Java ?

  • 1 toUpperCase
  • It is used to convert all the lowercase alphabet into uppercase alphabet.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.toUpperCase());
  }
 }
/*
### OUTPUT ###
EASY
*/
  • 2 toLowerCase
  • It is used to convert all the uppercase alphabet into lowercase alphabet.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.toLowerCase());
  }
 }
/*
### OUTPUT ###
easy
*/
  • 3 length
  • It is used to count the total number of character in string.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.length());
  }
 }
/*
### OUTPUT ###
4
because total number of character is 4
*/
  • 4 charAt
  • It is used to get single character at particular index.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.charAt(2)); 
  }
 }
/*
### OUTPUT ###
s
indexing starts from 0 so at index 2 s is present
*/
  • 5 startsWith
  • It is used to check prefix of a String
  • It returns boolean value(true/false).
  • If the given string begins with specified letter returns true otherwise returns false.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.startsWith("ea"));//false 
   System.out.println(s.startsWith("Ea"));//true
  }
 }
/*
### OUTPUT ###
false
true
*/
  • 6 endsWith
  • It is used to check the given string is ending with specified word or not.
  • It returns boolean value(true/false).
  • If the given string ends with specified letter returns true otherwise returns false.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.endsWith("sy"));//true 
   System.out.println(s.endsWith("sY"));//false
  }
 }
/*
### OUTPUT ###
true
false
*/
  • 7 compareTo
  • It is used to compare two string.
  • It returns zero or non-zero value.
  • If the both string are same returns zero otherwise returns non-zero.
//Example 1
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.compareTo("Easy"));
   System.out.println(s.compareTo("easy"));
  }
 }
/*
### OUTPUT ###
0
-32
*/

//Example 2:Login Program
import java.util.Scanner;
class EASY
 {
  public static void main(String[] args) 
  {
   Scanner in=new Scanner(System.in);
   String username,password;
   System.out.println("Enter username");
   username=in.next();
   System.out.println("Enter password");
   password=in.next();
   if(username.compareTo("abcd@gmail.com")==0&&password.compareTo("12345")==0)
   System.out.println("Login Success");
   else
   System.out.println("Login Failed!!!");
  }
 }
/*
### OUTPUT ###
Enter username
abcd@gmail.com
Enter password
12345
Login Success
*/
  • 8 equals
  • It is used to compare two string.
  • It returns boolean value(true/false).
  • If the both string are same returns true otherwise returns false.
//Example 1
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   System.out.println(s.equals("Easy"));
   System.out.println(s.equals("easy"));
  }
 }
/*
### OUTPUT ###
true
false
*/

//Example 2:Login Program
import java.util.Scanner;
class EASY
 {
  public static void main(String[] args) 
  {
   Scanner in=new Scanner(System.in);
   String username,password;
   System.out.println("Enter username");
   username=in.next();
   System.out.println("Enter password");
   password=in.next();
   //using equals function
   if(username.equals("abcd@gmail.com")&&password.equals("12345"))
   System.out.println("Login Success");
   else
   System.out.println("Login Failed!!!");
  }
 }
/*
### OUTPUT ###
Enter username
abcd@gmail.com
Enter password
12345
Login Success
*/
  • 9 toCharArray
  • It is used to convert the string into character array.
//Example 1
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   char ch[]=s.toCharArray();
   for(int i=0;i<ch.length;i++)
   System.out.println("character at "+i+" is "+ch[i]);
  }
 }
/*
### OUTPUT ###
character at 0 is E
character at 1 is a
character at 2 is s
character at 3 is y
*/
  • 10 reverse
  • It is used to reverse the character of string.
  • reverse function is defined inside StringBuffer.
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   String rev=new StringBuffer(s).reverse().toString();
   System.out.println("Original String="+s+"\nReverse String="+rev);
  }
 }
/*
### OUTPUT ###
Original String=Easy
Reverse String=ysaE
*/
  • 11 replace
  • It is used to replace the particular string with new string.
/*
Syntax:
replace(old char,new char)
*/
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy softwares is telecom training centre";
   //replace telecom with software
   String s1=s.replace("telecom", "software");
   System.out.println("Original String="+s+"\nUpdated String="+s1);
  }
 }
/*
### OUTPUT ###
Original String=Easy softwares is telecom training centre
Updated String=Easy softwares is software training centre
*/
  • 12 replaceAll
  • It is used to replace all the matching string with new string.
/*
Syntax:
replaceAll(old char,new char)
*/
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy softwares is software training centre";
   //replace all a  with @
   String s1=s.replaceAll("a", "@");
   System.out.println("Original String="+s+"\nUpdated String="+s1);
  }
 }
/*
### OUTPUT ###
Original String=Easy softwares is software training centre
Updated String=E@sy softw@res is softw@re tr@ining centre
*/
  • 13 replaceFirst
  • It replaces only first substring of the string that matches with new string.
/*
Syntax:
replaceFirst(old char,new char)
*/
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy softwares is software training centre";
   //replace only first a  with @
   String s1=s.replaceFirst("a", "@");
   System.out.println("Original String="+s+"\nUpdated String="+s1);
  }
 }
/*
### OUTPUT ###
Original String=Easy softwares is software training centre
Updated String=E@sy softwares is software training centre
*/
  • 14 getBytes
  • It is used to get the ASCII value of each alphabet,digit and special symbol of string.
/*
ASCII value of 
A=65,B=66,C=67...Z=90
a=97,b=98,c=99...z=122
*/
class EASY
 {
  public static void main(String[] args) 
  {
   String s="Easy";
   //passing string into byte array
   byte ar[]=s.getBytes();
   for (int i = 0; i < ar.length; i++) 
    {
    System.out.println(ar[i]);     
    }
  }
 }
/*
### OUTPUT ###
69
97
115
121
*/
  • 15 indexOf
  • It is used to get the index of particular character.
  • Suppose that the given character exists more than one time in the given string then indexOf function returns the index of letter which is first from the left.
class Easy
{  
 public static void main(String[] args) 
 {
   String s="Easy Softwares";
     System.out.println(s.indexOf("a"));
 }    
}
/*
### OUTPUT ###
1
because indexing starts from 0
*/
  • 16 lastIndexOf
  • Suppose that the given character exists more than one time in the given string then lastIndexOf function returns the index of letter which is last from the left.
class Easy
{  
 public static void main(String[] args) 
 {
   String s="Easy Softwares";
     System.out.println(s.lastIndexOf("a"));
 }    
}
/*
### OUTPUT ###
10
because indexing starts from 0
*/
  • 17 trim
  • It is used to remove unwanted spaces from the string.
class Easy
{  
 public static void main(String[] args) 
 {
   String s="               Easy";
     System.out.println("Before Trim");
     System.out.println(s);
     System.out.println("After Trim");
     System.out.println(s.trim());
 }    
}
/*
### OUTPUT ###
Before Trim
               Easy
After Trim
Easy
*/
  • 18 contains
  • It is used to match the specified sequence of character in the given string.
  • It returns boolean value(True/False).
  • If the given character matches with string returns true otherwise returns false.
class Easy
{  
 public static void main(String[] args) 
 {
   String s="Easy softwares is an ISO Certified Training Centre";
   System.out.println(s.contains("ISO")); 
 }    
}
/*
### OUTPUT ###
true
*/
  • 19 intern
  • It is used to copy one string into another.
class Easy
{  
 public static void main(String[] args) 
 {
   String s="Easy softwares";
   System.out.println(s);
   String s2=s.intern();
   System.out.println(s2); 
 }    
}
/*
### OUTPUT ###
Easy softwares
Easy softwares
*/
  • 20 valueOf
  • It is used to convert data type into string.
class Easy
{  
 public static void main(String[] args) 
 {
   int no=10;
   System.out.println(no+20);
   String s=String.valueOf(no);
   System.out.println(s+20); 
 }    
}
/*
### OUTPUT ###
30
1020
*/
  • 21 isEmpty
  • It is used to check given string is empty or not.
  • It returns boolean value(True/False).
class Easy
{  
 public static void main(String[] args) 
 {
   String s1="Easy";
   System.out.println(s1.isEmpty());
   String s2="";
   System.out.println(s2.isEmpty()); 
 }    
}
/*
### OUTPUT ###
false
true
*/
  • 22 substring
  • It returns the substring for given begin index.
class Easy
{  
 public static void main(String[] args) 
 {
   String s1="EasySoftwares";
   //substring(startIndex)
   System.out.println(s1.substring(4)); //Softwares
   //substring(startIndex,endString)
   System.out.println(s1.substring(4,8));//Soft
 }    
}
/*
### OUTPUT ###
Softwares
Soft
*/
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