6 Ways for Comparing two strings in Java

Safalta Expert Published by: Aryan Rana Updated Wed, 16 Nov 2022 11:40 PM IST

Highlights

A String is a term that describes a group of characters. They cannot be changed after being produced since they are immutable.

Table of Content
Java Comparison of Two Strings
Method String Equals
Equals String Ignore Case
Object = Method
Method For Comparing Strings

Double Equal To Operator Utilization


In many different fields, string manipulation can be incredibly beneficial. Data mining, text analytics, and data matching could all benefit from it. In this post, we'll concentrate on comparing two strings in Java for various string manipulation reasons.

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Java Comparison of Two Strings

A String is a class of characters that can be defined. They are unchangeable after creation because they are unchanging. As can be seen below, there are several ways to compare two strings in Java.


Method String Equals

The values contained in the strings are used to compare the strings.

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If the values of the two strings match, the procedure returns true; otherwise, it returns false.
 
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public class Main {
public static void main(String args[])
{
String str1 = new String("Rock");
String str2 = new String("Roll");
String str3 = new String("rock");
String str4 = new String("Rock");
String str5 = new String("Roll");
//comparing the strings
System.out.println("Comparing " + str1 + " and " + str2
+ " : " + str1.equals(str2));
System.out.println("Comparing " + str3 + " and " + str4
+ " : " + str3.equals(str4));
System.out.println("Comparing " + str4 + " and " + str5
+ " : " + str4.equals(str5));
System.out.println("Comparing " + str1 + " and " + str4
+ " : " + str1.equals(str4));
}
}


Output:

Comparing Rock & Roll: False

comparing rock and Rock: False

Comparing Rock & Roll: False

comparing Rock and Rock: True

Let's proceed with the second section of this article.


Equals String Ignore Case

The case of the string is not taken into account when this function compares the two strings ( lower or upper). If the values are both equal and not null, the result is true.
 
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public class Main {
public static void main(String args[])
{
String str1 = new String("Rock");
String str2 = new String("Roll");
String str3 = new String("rock");
String str4 = new String("Rock");
String str5 = new String("Roll");
//Comparing Strings
System.out.println("Comparing " + str1 + " and " + str2
+ " : " + str1.equalsIgnoreCase(str2));
System.out.println("Comparing " + str3 + " and " + str4
+ " : " + str3.equalsIgnoreCase(str4));
System.out.println("Comparing " + str4 + " and " + str5
+ " : " + str4.equalsIgnoreCase(str5));
System.out.println("Comparing " + str1 + " and " + str4
+ " : " + str1.equalsIgnoreCase(str4));
}
}


Output:

Comparing Rock & Roll: False

comparing rock with Rock: True

Comparing Rock & Roll: False

comparing Rock and Rock: True

Let's continue with the following section of this post about comparing two strings in Java,


Object = Method

The method returns true if the parameters are equal to one another, and false otherwise. The output is true if both of the given parameters are null. The output is false if any one input has a null value.
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import java.util.*;
public class Main {
public static void main(String args[])
{
String str1 = new String("Rock");
String str2 = new String("Roll");
String str3 = new String("Roll");
String str4 = null;
String str5 = null;
System.out.println("Comparing " + str1 + " and " + str2
+ " : " + Objects.equals(str1, str2));
System.out.println("Comparing " + str2 + " and " + str3
+ " : " + Objects.equals(str2, str3));
System.out.println("Comparing " + str1 + " and " + str4
+ " : " + Objects.equals(str1, str4));
System.out.println("Comparing " + str4 + " and " + str5
+ " : " + Objects.equals(str4, str5));
}
}


Output:

Comparing Rock & Roll: False

Comparing Roll and Roll: True

Comparing Rock and null: False

comparing null and null: True

Now, let's continue.


Method For Comparing Strings

The input strings are compared to one another in this procedure. Following the comparison, the value is as follows:
  • A positive value is returned if (str1>str2) is true.
  • 0 is given if (str1==str2) is true.
  • A negative value is returned if (str1str2) is true.
 

Code

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import java.util.*;
public class Main {
public static void main(String args[])
{
String str1 = new String("Rock");
String str2 = new String("Pop");
String str3 = new String("Roll");
String str4 = new String("Roll");
System.out.println("Comparing " + str1 + " and " + str2
+ " : " + str1.compareTo(str2));
//Comparing String 3 = String 4
System.out.println("Comparing " + str3 + " and " + str4
+ " : " + str3.compareTo(str4));
System.out.println("Comparing " + str2 + " and " + str4
+ " : " + str2.compareTo(str4));
}
}


Output:

Comparing Rock and Pop:2

Comparing Roll and Roll :0

Comparing Pop and Roll:-2

This brings us to the final bit of this comparing two strings in a Java article,


Double Equal To Operator Utilization

Avoid using this approach when comparing two string values. The following list highlights the key distinctions between the equals() and == operators:

While == is an operator, equals() is a method.

While the equals() technique is used for content comparison, the == operator is used for reference comparison.

Since the == operator determines whether two strings point to the same object or not, reference equality is checked rather than verified.

 

Code

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import java.util.*;
public class Main {
public static void main(String[] args)
{
String str1 = new String("Rock");
String str2 = new String("Rock");
System.out.println(str1 == str2);
System.out.println(str1.equals(str2));
}
}


Output:

False

True


The techniques described in the article give programmers of the Java programming language a thorough approach to comparing two strings.


 

How can two sets of strings be compared in Java?

Java's util. equals() function. The Set class is utilised to compare and validate the equivalence of an Object with a Set. If the sets are the same size and have the same number of elements, the function returns true.

Can you compare two strings in Java using ==?

Java compares two strings using the == operator, also referred to as the equality operator.

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