Java子類拋出的異常類型不能比父類拋出的異常類型更寬泛

  Java子類拋出的異常類型不能比父類拋出的異常類型更寬泛,只對非檢查異常有效。

  如下的例子會報錯，Exception爲受查異常。

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

class ParentException extends Exception {
    public ParentException(String message){
        super(message);
    }
}

class ChildrenException extends Exception {
    public ChildrenException(String message){
        super(message);
    }
}

class Parent{
    public void sayHello()throws ChildrenException{
        System.out.println("Hi");
        throw new ChildrenException("這樣下去不行不行");
    }
}

class Children extends Parent{
    public void sayHello()throws ParentException{
        System.out.println("Hi");
        throw new ParentException("這樣下去不行不行");
    }
}

public class a{
    public static void main(String[] args)  {
        Parent parent = new Parent();
        Children children = new Children();
        parent.sayHello();
        children.sayHello();
    }
}

  如下的例子不會報錯，RuntimeException爲非受查異常

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

class ParentException extends RuntimeException {
    public ParentException(String message){
        super(message);
    }
}

class ChildrenException extends RuntimeException {
    public ChildrenException(String message){
        super(message);
    }
}

class Parent{
    public void sayHello()throws ChildrenException{
        System.out.println("Hi");
        throw new ChildrenException("這樣下去不行不行");
    }
}

class Children extends Parent{
    public void sayHello()throws ParentException{
        System.out.println("Hi");
        throw new ParentException("這樣下去不行不行");
    }
}

public class a{
    public static void main(String[] args)  {
        Parent parent = new Parent();
        Children children = new Children();
        parent.sayHello();
        children.sayHello();
    }
}