相关疑难解决方法(0)

我似乎无法理解为什么当我在quarter对象上使用println方法时,它返回toString方法的值.我从来没有调用过toString方法为什么我得到返回值？

public class Main {
    public static void main(String[] args) {
        Quarter q = new Quarter();
        Nickel n = new Nickel();
        System.out.println(q);
        System.out.println(n);
    }
}

public abstract class Money {
    private int value;

    public Money(int v) {
        value=v;
    }

    public abstract int getValue();

    protected int myValue() {
        return value;
    }

    public abstract String toString();
}

public abstract class Coin extends Money {
    public Coin(int value) {
        super(value);
        System.out.println("I am a coin, my value is " + getValue());
    }
}

public …