java - 如何使我的班级能够投射整数

Question

我对如何将我的课程转换为Integer. 例子：

public class IntegerField extends Field {
    private Integer value;
    public IntegerField(Integer value) {
        super();
        this.value = value;
    }
    public int intValue() {
        return value;
    }
}

我该怎么做：

IntegerField a = new IntegerField(8);
Integer b = (Integer) a;

谢谢！

Answer 1

No. You can't define your own conversion operators in Java. However, it's simple to add a method:

public class IntegerField extends Field {
    private Integer value;
    public IntegerField(Integer value) {
        super();
        this.value = value;
    }

    public Integer toInteger() {
        return value;
    }
}

...

IntegerField a = new IntegerField(8);
Integer b = a.toInteger();

Why would you prefer a cast?

(Note that I've removed the intValue method which would throw an exception if value is null. The caller of toInteger can always convert to int if they want that behaviour.)

Answer 2

整数 b = (整数) a; --- 不正确，因为 value 是私有的，你必须写一个方法来获取 value，Integer b = a.intValue();