Java.Java8.What is the functional interface BiPredicate?

Let’s dive into BiPredicate<T, U>, a functional interface used to evaluate a boolean condition based on two inputs.

✅ BiPredicate<T, U>

@FunctionalInterface
public interface BiPredicate<T, U> {
    boolean test(T t, U u);
}

Takes two arguments of types T and U

Returns a boolean

It’s like Predicate<T>, but with two inputs

BiPredicate<String, Integer> isLongerThan = (str, length) -> str.length() > length;

System.out.println(isLongerThan.test("banana", 5)); // true
System.out.println(isLongerThan.test("cat", 5));    // false

🔧 Real Use Case: Validation Logic

You might use it to validate input pairs:

BiPredicate<String, String> isLoginMatch = (username, password) ->
    "admin".equals(username) && "1234".equals(password);

System.out.println(isLoginMatch.test("admin", "1234")); // true

🔗 Combining with .and(), .or(), .negate()

Just like Predicate, BiPredicate supports chaining:

BiPredicate<Integer, Integer> bothPositive = (a, b) -> a > 0 && b > 0;
BiPredicate<Integer, Integer> sameParity = (a, b) -> (a % 2) == (b % 2);

BiPredicate<Integer, Integer> combined = bothPositive.and(sameParity);

System.out.println(combined.test(4, 2));  // true
System.out.println(combined.test(4, -2)); // false (not both positive)

✅ Summary

Interface	Input Types	Return Type	Use Case Example
BiPredicate<T,U>	T, U	boolean	(s, n) -> s.length() > n, login validation