[Lambda] 기본형 함수형 인터페이스 : ToIntFunction<T>, ToIntBiFunction<T, U> 등

리턴타입 : int, double, long 

파라미터 타입 : 제네릭 

 

ToIntFunction<T> : public int applyAsInt(T t)

ToIntBiFunction<T, U> : public int applyAsInt(T t, U u)

 

ToDoubleFunction<T> : public double applyAsDouble(T t)

ToDoubleBiFunction<T, U> : public double applyAsDouble(T t, U u)

 

ToLongFunction<T> : public long applyAsLong(T t)

ToLongBiFunction<T, U> : public long applyAsLong(T t, U u)

 

import java.util.function.ToIntBiFunction;
import java.util.function.ToIntFunction;

public class ToIntFunctionExam {

    public static void main(String[] args) {

        ToIntFunction<String> toIntFunction = new ToIntFunction<String>() {
            @Override
            public int applyAsInt(String value) {
                return Integer.parseInt(value);
            }
        };

        boolean result = Integer.class.isInstance(toIntFunction.applyAsInt("1234"));
        System.out.println(result);

        ToIntBiFunction<String,String> toIntBiFunction = new ToIntBiFunction<String, String>() {
            @Override
            public int applyAsInt(String s1, String s2) {
                return Integer.parseInt(s1+s2);
            }
        };

        result = Integer.class.isInstance(toIntBiFunction.applyAsInt("12","34"));
        System.out.println(result);
        
    }
}