Java String equalsIgnoreCase()

The Java String class equalsIgnoreCase() method compares the two given strings on the basis of the content of the string irrespective of the case (lower and upper) of the string. It is just like the equals() method but doesn't check the case sensitivity. If any character is not matched, it returns false, else returns true.

Signature

Parameter

str : another string i.e., compared with this string.

Returns

It returns true if characters of both strings are equal, ignoring case otherwise false.

Internal implementation

public boolean equalsIgnoreCase(String anotherString) {  
       return (this == anotherString) ? true  
               : (anotherString != null)  
               && (anotherString.value.length == value.length)  
               && regionMatches(true, 0, anotherString, 0, value.length);  
   }  

It is obvious from looking at the implementation that the equalsIgnoreCase() method is invoking the regionMatches() method. It makes the equalsIgnoreCase() method case-insensitive. The signature of the regionMatches() method is mentioned below.

public boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)

The regionMatches() method parses five parameters. The first parameter ignoreCase is set to true in the above implementation. Thus, when the method is executed, it checks whether the ignoreCase flag is true or not. If yes, then one character each from both the strings is taken and then compared. If the comparison gives a false value, then both the character is converted to upper case and then checked if the comparison still gives a false value, then both the characters are converted to a lower case and then compared. If the comparison gives the true value, then both the strings have equal contents; otherwise, not. Code Snippet of the discussed comparison is mentioned below.

while (toffset < last) 
{
char ch1 = getChar(value, toffset++);
char ch2 = getChar(other, ooffset++);
if (ch1 == ch2) 
{
continue;
}
// convert each character to uppercase and 
// then make the comparison.
// If the comparison yeilds a true value, 
// then next pair of characters should be scanned
char uCh1 = Character.toUpperCase(ch1);
char uCh2 = Character.toUpperCase(ch2);
if (uCh1 == u2) 
{
continue;
}

// convert each character to lowercase and 
// then make the comparison.
// If the comparison yeilds a true value, 
// then next pair of characters should be scanned
// Otherwise, return false.
if (Character.toLowerCase(uCh1) == Character.toLowerCase(uCh2)) 
{
continue;
}
return false;
}

// reaching here means the content of both the strings 
// are the same after ignoring the case sensitiveness
return true;

One may argue that if we made a comparison after converting to uppercase, then why do we need an extra comparison by converting characters to the lowercase. The reason behind this is to provide to the requirement of Georgian alphabets. Conversion in uppercase does not work properly for the Georgian alphabets, as they have some strange rules about the case conversion. Therefore, one extra comparison, by converting characters to the lowercase, is required.

Java String equalsIgnoreCase() Method Example

FileName: EqualsIgnoreCaseExample.java

public class EqualsIgnoreCaseExample{
public static void main(String args[]){
String s1="javatpoint";
String s2="javatpoint";
String s3="JAVATPOINT";
String s4="python";
System.out.println(s1.equalsIgnoreCase(s2));//true because content and case both are same
System.out.println(s1.equalsIgnoreCase(s3));//true because case is ignored
System.out.println(s1.equalsIgnoreCase(s4));//false because content is not same
}}

Test it Now

Output:

true
true
false

Java String equalsIgnoreCase() Method Example 2

Let's see an example where we are testing string equality among the strings.

FileName: EqualsIgnoreCaseExample2.java

import java.util.ArrayList;
public class EqualsIgnoreCaseExample2 {
	public static void main(String[] args) {
		String str1 = "Mukesh Kumar";
		ArrayList<String> list = new ArrayList<>();
		list.add("Mohan"); 
		list.add("Mukesh");
		list.add("RAVI");
		list.add("MuKesH kuMar");
		list.add("Suresh");
		for (String str : list) {
			if (str.equalsIgnoreCase(str1)) {
				System.out.println("Mukesh kumar is present");
			}
		}
	}
}

Output: