equals and equalsIgnoreCase
- Java course
- Beginner
- Lesson 31/116
- 4 min
Learn string comparison with equals().
equals and equalsIgnoreCase
To compare the content of two Strings use equals. The == operator compares references, so for Strings equals is preferred.
String a = "Hello";
String b = "Hello";
System.out.println(a.equals(b)); // true
System.out.println(a.equalsIgnoreCase(b)); // true (case insensitive)equalsIgnoreCase ignores case differences. "JAVA".equalsIgnoreCase("java") returns true.
The most common mistake in String comparison is using ==.
Practice Compare with equals
Write a Main class with a main method. Assign "Hello" to String a and "hello" to String b. Print a.equals(b) and a.equalsIgnoreCase(b) with println.
Sample solution
public class Main {
public static void main(String[] args) {
String a = "Hello";
String b = "hello";
System.out.println(a.equals(b));
System.out.println(a.equalsIgnoreCase(b));
}
}Expected output
false true
Why does == not work?
Strings are reference types. == checks whether two variables point to the same object, not whether their content matches.
String a = "Hello";
String b = new String("Hello");
System.out.println(a == b); // false!
System.out.println(a.equals(b)); // trueJava pools (interns) some Strings, so == may sometimes return true. But this is not reliable; always use equals.
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match the methods
| Term | Meaning |
|---|---|
equals |
Content equal |
equalsIgnoreCase |
Case insensitive |
== |
Reference compare |
!= |
Not equal |
2 What does "JAVA".equalsIgnoreCase("java") return?
- false
- true Correct answer
- null
- Error
Explanation: equalsIgnoreCase ignores case differences.
3 Complete the equals call
boolean same = a.____(b);boolean same = a.equals(b);Explanation: a.equals(b) compares the content of two strings.