What is a Java predicate?
The predicate is a predefined functional interface in Java defined in the java.util.Function package. It helps with manageability of code, aids in unit-testing, and provides various handy functions.
Predicate methods
Let’s have a look at a few methods that the Java predicate provides.
1. test(T t)
It evaluates the predicate on the value passed to this function as the argument and then returns a boolean value. Take a look at the example below:
import java.util.function.Predicate;class testDemo {public static void main(String[] args){Predicate<Integer> greater_than = x -> (x > 10);// calling test method of the predicateSystem.out.println(greater_than.test(11));}}
2. isEqual(Object t)
It returns a predicate that tests if two objects are equal. Take a look at the example below:
import java.util.function.Predicate;class isEqualDemo {public static void main( String args[] ) {Predicate<String> pred = Predicate.isEqual("Educative");System.out.println(pred.test("educative "));}}
3. and(Predicate P)
It returns a composed predicate that represents a logical AND of the outputs coming from both predicates. Take a look at the example below:
import java.util.function.Predicate;class andDemo {public static void main(String[] args){Predicate<Integer> grt_10 = x -> (x > 10);Predicate<Integer> less_100 = x -> (x < 100);// composing two predicates using andSystem.out.println(grt_10.and(less_100).test(60));}}
4. or(Predicate P)
It returns a composed predicate that represents a logical OR of the outputs coming from both predicates. Take a look at the example below:
import java.util.function.Predicate;class andDemo {public static void main(String[] args){Predicate<Integer> eq_10 = x -> (x == 10);Predicate<Integer> grt_20 = x -> (x > 20);// composing two predicates using andSystem.out.println(eq_10.or(grt_20).test(21));}}
5. negate()
It returns a predicate that represents the logical negation of the respective predicate. Take a look at the example below:
import java.util.function.Predicate;class testDemo {public static void main(String[] args){Predicate<Integer> greater_than = x -> (x > 10);// calling negate method of the predicateSystem.out.println(greater_than.negate().test(11));}}
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