抛出线程陷阱

Question

My problem is I cannot make the inner catch throw an exception. Here I want ex to be thrown to the outer catch.

Runnable(){

public void run(){
try{
    try{
       }catch(Exception ex){
        System.out.println("Inner");
        throw ex; //I get an error here
    }
}catch(Exception e){
    System.out.println("Outer");
}}

Error message: Unreported Exception must be caught, declared to be thrown

Answer 1

Put the block in a function .....

private void myFunction() throws Exception {

    try{
       }catch(Exception ex){
        System.out.println("Inner");
        throw ex; //I get an error here
    }
}

Then call it from your code block

Runnable(){

public void run(){
    try{
        myFunction();
    }catch(Exception e){
    System.out.println("Outer");
}}

Answer 2

This seems to function just fine. Making nested try-catch blocks is considered bad practice.

public class Test implements Runnable {

public void run() {
    try {
        try {
            throw new IOException("bad"); //throw something here
        } catch (Exception ex) {
            System.out.println("Inner");
            throw ex; 
        } finally  {

        }
    } catch (Exception e) {
        System.out.println("Outer");
    }
}


public static void main(String[] args) {
    new Test().run();
}

}

// PRINTS: 
// Inner
// Outer

Answer 3

try this.

Callable(){

public void call(){
try{
try{
   }catch(Exception ex){
    System.out.println("Inner");
    throw ex; //I get an error here
}
}catch(Exception e){
System.out.println("Outer");
}}