Java Comparison Operators

Comparison operators take two operands and produce a boolean. Java has six of them — equal, not-equal, and the four relational operators. The catch is that == does something different on primitives than on objects, which is the single most common source of beginner bugs.

The six operators

Each yields a boolean you can use in an if test, a loop condition, or as the value of a variable:

int score = 85;
boolean passed = score >= 60;        // true
boolean perfect = score == 100;      // false
boolean failed = !(score >= 60);     // false

== on primitives

For primitive types, == compares the value:

int a = 5;
int b = 5;
System.out.println(a == b);    // true

double x = 0.1 + 0.2;
double y = 0.3;
System.out.println(x == y);    // false — IEEE 754 rounding

The floating-point case is a reminder: don't compare double values for exact equality. Test that they're within a small tolerance:

System.out.println(Math.abs(x - y) < 1e-9);   // true

== on objects — identity, not equality

For reference types, == compares references — whether the two variables point at the same object in memory. Two distinct objects with identical contents are not ==:

String s1 = new String("hello");
String s2 = new String("hello");

System.out.println(s1 == s2);          // false — different objects
System.out.println(s1.equals(s2));     // true  — same contents

The rule of thumb: for objects, always use .equals() to compare contents.

if (input.equals("quit")) { ... }      // correct
// if (input == "quit") { ... }        // works by coincidence, don't rely on it

The == "quit" form sometimes returns true because Java de-duplicates string literals — the same literal compiles to the same object. But that's an implementation detail, not a guarantee.

Objects.equals — null-safe

If either side might be null, obj.equals(other) throws NullPointerException. Use Objects.equals instead — it handles null on either side:

import java.util.Objects;

String a = null;
String b = "hello";

System.out.println(Objects.equals(a, b));   // false (no NPE)
System.out.println(Objects.equals(a, null)); // true

Comparing wrapper objects

Wrapper types (Integer, Long, etc.) follow the object rule — == compares references, not values:

Integer x = 200;
Integer y = 200;
System.out.println(x == y);         // false (usually)
System.out.println(x.equals(y));    // true

(Values from -128 to 127 are cached, so Integer x = 100; Integer y = 100; x == y happens to be true — but that's a JVM quirk, not the language rule. Don't rely on it.)

Comparing for ordering — .compareTo

<, >, <=, >= only work on primitives. To compare objects for ordering, use the Comparable.compareTo method (returns negative, zero, or positive):

String a = "apple";
String b = "banana";

System.out.println(a.compareTo(b));   // negative — "apple" < "banana"
System.out.println(a.compareTo(a));   // 0
System.out.println(b.compareTo(a));   // positive

Integer, Long, String, LocalDate, and most "natural" types implement Comparable. Custom ordering uses Comparator — covered in Comparable and Comparator.

A demonstration

What's next

Java Logical Operators — combining boolean expressions with &&, ||, and !.

Practice