Deep Dive into Java 8 Predicate Interface

Predicate is a Functional Interface (an Interface with only one abstract method) that was introduced in Java 8 in the java.util.function package.

Method	Description	Return Type	Exceptions	Input Type	Added in JDK
test(T t)	Evaluates this predicate on the given argument.	boolean		T	Java 8
and(Predicate<? super T> other)	Returns a composed predicate that represents a short-circuiting logical AND of this predicate and another.	Predicate<T>	NullPointerException if other is null	T	Java 8
negate()	Returns a predicate that represents the logical negation of this predicate.	Predicate<T>		N/A	Java 8
or(Predicate<? super T> other)	Returns a composed predicate that represents a short-circuiting logical OR of this predicate and another.	Predicate<T>	NullPointerException if other is null	T	Java 8
isEqual(Object targetRef)	Returns a predicate that tests if two arguments are equal according to Objects.equals(Object, Object).	Predicate<T>		T	Java 8
not(Predicate<? super T> target)	Returns a predicate that is the negation of the supplied predicate.	Predicate<T>	NullPointerException if target is null	T	Java 11

The test() is the abstract method that returns a boolean by predicting whether the performed condition is true or not for the provided generic type argument T.

Example:

    public static void main(String[] args) {

        Predicate<Integer> evenOrOdd = num -> num % 2 == 0;

        int testNumberForEvenOdd = 12;
        boolean isEven = evenOrOdd.test(testNumberForEvenOdd);
        System.out.println(testNumberForEvenOdd + " is Even: " + isEven);

    }

Output: