Question on switch being unreachable

[manda prasad]

The below first question is from Dan's ,and it raises a compile time error,saying that switch is unreachable when nested try(second) does not execute.Please find another program below:

 
class Level1Exception extends Exception {}
class Level2Exception extends Level1Exception {}
class Level3Exception extends Level2Exception {}
class Purple {
  public static void main(String args[]) {
    int a,b,c,d,f,g,x;
    a = b = c = d = f = g = 0;
    x = 1;
    try {
      throw new Level1Exception();
      try {
        switch (x) {
          case 1: throw new Level1Exception();
          case 2: throw new Level2Exception();
          case 3: throw new Level3Exception();
      } a++; }
      catch (Level2Exception e) {b++;}
      finally {c++;}
    }
    catch (Level1Exception e) { d++;}
    catch (Exception e) {f++;}
    finally {g++;}
    System.out.print(a+","+b+","+c+","+d+","+f+","+g);
}}
 

 

class Example {
public static void main(String args[]) {
byte x=4;
if(x>8) {

switch(x) {
case 1:System.out.println("sd");
case 2:System.out.println("sdd");
case 4: System.out.println("sdss");
default : System.out.println("sdasda");
}}
}
}

why doesn't this program raise the same error, when does the switch block gets unreachable.

[kapil munjal]

Hi Prasad,

your first Example of Dan's exam....

If you look at it, you will find that in the first try block, the first statement is "throw new Level1Exception();". so whenever that block runs, it throws and exception and it directly reaches to the corresponding catch block. So avoiding the new try block inside the try block. So this way, the second try block will never reach in any condition. This is why it throws an error while compilation.

your second example.........

You always reach inside the switch block, and execute one of the cases. Its completely a different issue!!!

The difference between these two conditions is that first is related to Exceptions and the other one is a condition statement.

I hope it helps
Kaps