String Comparision

String comparison in Java

We can compare two given strings on the basis of content and reference.

It is used in authentication (by equals() method), sorting (by compareTo() method), reference matching (by == operator) etc.


There are three ways to compare String objects:

1. By equals() method
2. By = = operator
3. By compareTo() method

1) By equals() method
equals() method compares the original content of the string.It compares values of string for equality.String class provides two methods:

public boolean equals(Object another){} compares this string to the specified object.
public boolean equalsIgnoreCase(String another){} compares this String to another String, ignoring case.

class Teststringcomparison1{
public static void main(String args[]){

String s1="Sachin";
String s2="Sachin";
String s3=new String("Sachin");
String s4="Saurav";

System.out.println(s1.equals(s2));  //true
System.out.println(s1.equals(s3));  //true
System.out.println(s1.equals(s4));  //false
}
} 

Output:

true true false


//Example of equalsIgnoreCase(String) method
class Teststringcomparison2{
public static void main(String args[]){

String s1="Sachin";
String s2="SACHIN";

System.out.println(s1.equals(s2));  //false
System.out.println(s1.equalsIgnoreCase(s3));  //true
}
}
Output:

false 

true

2) By == operator
The = = operator compares references not values.

Example of == operator

class Teststringcomparison3 {
public static void main(String args[]) {

String s1="Sachin";
String s2="Sachin";
String s3=new String("Sachin");

System.out.println(s1==s2);     //true (because both refer to same instance)
System.out.println(s1==s3);    //false(because s3 refers to instance created in nonpool)
}
}
 

Output:

true 

false

3) By compareTo() method:
compareTo() method compares values and returns an int which tells if the values compare less than, equal, or greater than.
Suppose s1 and s2 are two string variables.If:

s1 == s2 :0
s1 > s2 :positive value
s1 < s2 :negative value

Example of compareTo() method:

class Teststringcomparison4{
public static void main(String args[]){

String s1="Sachin";
String s2="Sachin";
String s3="Ratan";

System.out.println(s1.compareTo(s2));     //0
System.out.println(s1.compareTo(s3));    //1(because s1>s3)
System.out.println(s3.compareTo(s1));   //-1(because s3 < s1 )
}
}

Output:

0 

1

-1