IntPredicate interface

IntPredicate is a Functional Interface added in java 8 and is a specialization of java Predicate for integer values.

IntPredicate represents an expression used to check integer values and returns true or false if the values match or not respectively.

IntPredicate works for integer values only.

Creating IntPredicate
As stated above, IntPredicate is a Functional Interface and hence it can be represented as a Lambda expression as shown below.

Here, IntPredicate is assigned a Lambda expression which checks if its argument is greater than 20. num is a variable that is local to Lambda expression and need not be declared before using it.

IntPredicate has a single method test() which takes an integer argument and test this value against the predicate condition. Example,

IntPredicate greaterThan = num -> num > 20;
boolean result = greaterThan.test(50); // returns true

In this example, test() will check if 50 is greater than 20.
Chaining IntPredicate
It is possible to check complex conditions by chaining Predicates such as checking if a number lies between a range, less than or equal to a threshold etc.

IntPredicate has methods such as and(), or() that allow combining multiple predicates together. This chaining works the same way as using logical AND(&&) or OR(||) operators.

Example, suppose you want to check if a number lies between 100 and 999. With predicate chaining, this can be done as below.

IntPredicate lower = num -> num >= 100;
IntPredicate higher = num -> num <= 999;
IntPredicate range = lower.and(higher);
boolean result = range.test(500);  // returns true

and() combines the predicates and the condition will evaluate true only when both the predicates return true.
Similarly, or() method is also used to combine predicates. In that case, if any one predicate returns true, the result of evaluation is true.
IntPredicate negate
IntPredicate has a negate() method which is used to reverse its result. It is similar to applying a NOT(!) before a condition.

Example, if you want to check if a number is greater than 0, then using negate(), it can be written as

// predicate for greater than 0
IntPredicate positive = num -> num > 0;
// reverse it
boolean result = positive.negate().test(5); // returns false

Note that IntPredicate is a Functional Interface having only one abstract method test(). All other methods such as and(). or(), negate() are default interface methods which are defined in the interface itself.

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