JAVA函数式编程尝试实现

JAVA函数式编程尝试实现

接口

public interface Func {
	public Object invoke(Object ...o);
}

MAP

import java.util.Arrays;
public class Test {
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Object[] arr = new Object[]{1, 2, 3, 4, 5};
		map(arr, new Func() {
			@Override
			public Object invoke(Object ...o) {
				return (Integer)o[0] * 2;
			}
		});
		System.out.println(Arrays.toString(arr));//output [2, 4, 6, 8, 10]
	}
	public static void map(Object[] arr, Func function) {
		for (int i = 0; i < arr.length; i++) {
			arr[i] = function.invoke(arr[i]);
		}
	}
	
}

reduce

public class Test2 {
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Object sum = sum(new Object[]{0, 1, 2, 3, 4});
		Object str = join(new Object[]{0, 1, 2, 3, 4});
		System.out.println(sum);//output 10
		System.out.println(str);//output 01234
	}
	private static Object join(Object[] objects) {
		return reduce(objects, "", new Func() {
			@Override
			public Object invoke(Object... o) {
				return o[0].toString() + o[1];
			}
		});
	}
	public static Object sum(Object[] arr) {
		return reduce(arr, 0, new Func() {
			@Override
			public Object invoke(Object ...o) {
				return (Integer)o[0] + (Integer)o[1];
			}
		});
	}
	private static Object reduce(Object[] arr, Object init, Func f) {
		Object sum = init;
		for (int i = 0; i < arr.length; i++) {
			sum = f.invoke(sum, arr[i]);
		}
		return sum;
	}
}