IOException与RuntimeException Java(IOException vs RuntimeException Java)

class Y {
    public static void main(String[] args) throws RuntimeException{//Line 1
        try {
            doSomething();
        }
        catch (RuntimeException e) {
            System.out.println(e);
        }
    }
    static void doSomething() throws RuntimeException{ //Line 2
        if (Math.random() > 0.5) throw new RuntimeException(); //Line 3
        throw new IOException();//Line 4
    }
}
 
 当我抛出两种类型的异常（Line4中的IOException和Line3中的RunTimeException）时，我发现我的程序不会编译，直到我在第1行和第2行的我的throws子句中指出“IOException”。 
 
 而如果我将“throws”反转为指示抛出IOException，则程序确实会成功编译，如下所示。 
 
class Y {
    public static void main(String[] args) throws IOException {//Line1
        try {
            doSomething();
        }
        catch (RuntimeException e) {
            System.out.println(e);
        }
    }
    static void doSomething() throws IOException {//Line 2
        if (Math.random() > 0.5) throw new RuntimeException();//Line 3
        throw new IOException();//Line 4
    }
}
 
 为什么我应该总是使用“抛出”IOException，即使RuntimeException也被抛出（第3行）？ 

class Y {
    public static void main(String[] args) throws RuntimeException{//Line 1
        try {
            doSomething();
        }
        catch (RuntimeException e) {
            System.out.println(e);
        }
    }
    static void doSomething() throws RuntimeException{ //Line 2
        if (Math.random() > 0.5) throw new RuntimeException(); //Line 3
        throw new IOException();//Line 4
    }
}
 
When I throw two types of exception (IOException in Line4 and RunTimeException in Line3), I found that my program does not compile until I indicate "IOException" in my throws clauses in Line 1 & Line 2.
 
Whereas if I reverse "throws" to indicate IOException being thrown, the program does compile successfully as shown below.
 
class Y {
    public static void main(String[] args) throws IOException {//Line1
        try {
            doSomething();
        }
        catch (RuntimeException e) {
            System.out.println(e);
        }
    }
    static void doSomething() throws IOException {//Line 2
        if (Math.random() > 0.5) throw new RuntimeException();//Line 3
        throw new IOException();//Line 4
    }
}
 
Why should I always use "throws" for IOException even though RuntimeException is also thrown (Line 3) ?

原文：https://stackoverflow.com/questions/18416511