Java8 Function和BiFunction

深入理解和使用Function

public static void main(String[] args) {        //这个例子讲解Function中compose和andThen的区别        Test09Function test = new Test09Function();        int result = test.functionCompose(10, value -> value * 2, value -> value * value);        System.out.println("result = [" + result + "]");        int result2 = test.functionAndThen(10, value -> value * 2, value -> value * value);        System.out.println("result2 = [" + result2 + "]");        System.out.println("---------------------------");        /**         *  我们调用Function的apply(a)可以传入一个参数得到一个结果，但是这个类无法做到输入2个参数，得到一个结果，         *  BiFunction可以做到这一点。Bi==Bidirectional双向的意思         */        int result3 = test.biFunctionCaculate(30, 20, (value1, value2) -> value1 + value2);        System.out.println("result3 = [" + result3 + "]");        int result4 = test.biFunctionCaculate(30, 20, (value1, value2) -> value1 - value2);        System.out.println("result4 = [" + result4 + "]");        int result5 = test.biFunctionAndThen(30, 20, (value1, value2) -> value1 - value2, value -> value * value);        System.out.println("result5 = [" + result5 + "]");    }    public int functionCompose(int a, Function<Integer, Integer> function1, Function<Integer, Integer> function2){        //(V v) -> apply(before.apply(v));        // 先应用function2的apply，并将结果作为参数再应用function1的apply        return function1.compose(function2).apply(a);    }    public int functionAndThen(int a, Function<Integer, Integer> function1, Function<Integer, Integer> function2){        //(T t) -> after.apply(apply(t))        // 先应用function1的apply，并将结果作为参数再应用function2的apply        return function1.andThen(function2).apply(a);    }    public int biFunctionCaculate(int a, int b, BiFunction<Integer, Integer, Integer> biFunction){        return biFunction.apply(a, b);    }    //BiFunction没有compose方法    /*@Deprecated    public int biFunctionCompose(int a, int b, BiFunction<Integer, Integer, Integer> biFunction, Function<Integer, Integer> function){        //return biFunction.compose(function).apply(a, b);    }*/    public int biFunctionAndThen(int a, int b, BiFunction<Integer, Integer, Integer> biFunction, Function<Integer, Integer> function){        return biFunction.andThen(function).apply(a, b);    }