Example of a Functional TriFunction interface and implementation (with Java 8 Lambdas)

TriFunction.java

package sample.function;

/**
 * Example of TriFunction
 * 
 * @author Andre Dias
 * @since 2017-08-12
 */
@FunctionalInterface
public interface TriFunction<F, S, T, R> {
	
	public R apply(F first, S second, T third);
  
}

TriFunctionIntegerAddImpl.java

package sample.function.tri;

/**
 * @see TriFunction 'Functional Interface' implementation example.
 * 
 * @author Andre Dias
 * @since 2017-08-12
 */
public class TriFunctionIntegerAddImpl implements TriFunction<Integer, Integer, Integer, Integer>{

	/**
	 * Addition (as default).
	 * 
	 * @see sample.function.tri.TriFunction#apply(java.lang.Object, java.lang.Object, java.lang.Object)
	 */
	public Integer apply(Integer first, Integer second, Integer third) {
		return first.intValue() + second.intValue() + third.intValue();
	}
	
	public static void main(String[] args) {
		
		executeAsUsual(); // Add Result: 6
		
		executeAsLambda(); // Multiply Result: 60
	}
	
	private static void executeAsUsual() {
		System.out.println(new TriFunctionIntegerAddImpl().apply(1, 2, 3));		
	}
	
	private static void executeAsLambda() {
		
		/*
		 * Create lambda (change default behavior - now multiply)
		 */
		TriFunction<Integer, Integer, Integer, Integer> triMultiply = (a, b, c) -> (a * b * c);

		/*
		 * Check it
		 */
		System.out.println(triMultiply.apply(10, 2, 3));		
	}
}