Java:基于用户输入的运行方法？

Question

假设我有三种方法

method1()
method2()
method3()

并且我让用户输入与他们想要运行的方法相对应的数字，有没有办法直接从他们的输入运行它？即，不要使用类似的 if 语句

System.out.println("Which method would you like to run? 1/2/3");
String input = reader.readLine();
if(input == 1){method1();}
if(input == 2){method2();}
...

等等。相反，能够拥有类似的东西

System.out.println("Which method would you like to run? 1/2/3");
String input = reader.readLine();
method(input)();

？

Answer 1

是的，您可以通过使用如下界面来实现这一点:

interface A {
    void run();
}

public void method1() {}

public void method2() {}

public void mainMethod(String[] args) {
    // Initialise the method map - note, you only have to do this once
    // So, this initialisation code can go into a constructor
    // And mothodMap can be declared as a final instance variable.
    A methodOne = new A() { @Override public void run() { method1(); } };
    A methodTwo = new A() { @Override public void run() { method2(); } };

    Map<Integer, A> methodMap = new HashMap<>();
    methodMap.put(1, methodOne);
    methodMap.put(2, methodTwo);

    Integer input = /* get it from user*/ 1;
    A aMethod = methodMap.get(input);
    aMethod.run();

}