源码基于Groovy程序设计一书中的第三章第6小姐

java中的多态

基类

public class Employee {
    public void raise(Number amount){
        System.out.println("Employee got raise");
    }
}

子类

import java.math.BigDecimal;

public class Executive extends Employee {
    @Override
    public void raise(Number amount) {
        System.out.println("Executive got raise");
    }
    public void raise(BigDecimal amount) {
        System.out.println("Executive got BigDecimal raise");
    }
}

主类

import java.math.BigDecimal;

public class Test {
    public static void giveRaise(Employee employee) {
        // 由于是基类的定义，在运行时调用的方法必须接受Number作为参数
        employee.raise(new BigDecimal(10000.00));
    }

    public static void main(String[] args) {
        giveRaise(new Employee());
        giveRaise(new Executive());
    }
}

输出

Employee got raise
Executive got raise

在groovy中使用多态

void giveRaise(Employee employee){
    employee.raise(new BigDecimal(10000.00))
}
giveRaise new Employee()
giveRaise new Executive()

输出

Employee got raise
Executive got BigDecimal raise