Add equalsIgnoreCase to the file (#27662)

The function equalsIgnoreCase() is also used for comparing the equality of 2 strings.

guide/english/java/equality/index.md

@@ -64,5 +64,17 @@ For example, the `java.util.Set` interface specifies that a `Set`'s `equals()` m
 
 However, if a class does not override the default `equals()` implementation, the default implementation will apply, which simply uses the `==` operator to compare the two objects.
 
+## The `.equalsIgnoreCase()` Method
+
+This built-in function in java is used to compare the equality of 2 strings return true or false depending on the match but this function does not see if the characters are in upper case or in lower case.
+Example:
+
+```java
+String s1="DEMO for Equality";
+String s2="Demo for equality";
+System.out.println(s1.equals(s2));      //false
+System.out.println(s1.equalsIgnoreCase(s2));    //true
+```
+
 #### More Information:
 - [Oracle Java Docs : Equality Operators](https://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.21)