1、使用BinaryOperator<Integer>和forEach实现代码
BinaryOperator<Integer> add = (a, b) -> a + b;//lambda a, b : a + b
BinaryOperator<Integer> sub = (a, b) -> a - b;//lambda a, b : a - b
// 创建一个新的Map,接受符号和相应的BinaryOperator
// 相当于 = {"+" : lambda a, b : a + b, "-" : lambda a, b : a - b}
Map<String, BinaryOperator<Integer>> signs = Map.of("+", add, "-", sub);
int a = 5; // a = 5
int b = 3; // b = 3
//循环遍历map并应用操作
signs.values().forEach(v -> System.out.println(v.apply(a, b)));
输出结果:
8
2
注意:Map.of("+", add, "-", sub);
用的是Java 10,如果Java 9+可以使用下面代码:
Map<String, BinaryOperator<Integer>> signs = new HashMap<>();
signs.put("+", add);
signs.put("-", sub);
2、代码优化
更好使用IntBinaryOperator
来避免装箱,可以使用下面写法的代码:
// signs = {"+" : lambda a, b : a + b, "-" : lambda a, b : a - b}
Map<String, IntBinaryOperator> signs = Map.of("+", (a, b) -> a + b, "-", (a, b) -> a - b);
int a = 5; // a = 5
int b = 3; // b = 3
// for i in signs.keys(): print(signs[i](a,b))
signs.values().forEach(v -> System.out.println(v.applyAsInt(a, b)));