Java Tutorial/Statement Control/try catch

An example of nested try statements.

   <source lang="java">

class NestTry {

 public static void main(String args[]) {
   try {
     int a = args.length;
     int b = 42 / a;
     System.out.println("a = " + a);
     try {
       if (a == 1)
         a = a / (a - a); // division by zero
       if (a == 2) {
         int c[] = { 1 };
         c[42] = 99; // generate an out-of-bounds exception
       }
     } catch (ArrayIndexOutOfBoundsException e) {
       System.out.println("Array index out-of-bounds: " + e);
     }
   } catch (ArithmeticException e) {
     System.out.println("Divide by 0: " + e);
   }
 }

}</source>

Catch different Exception types

   <source lang="java">

class MyException extends Exception {

 MyException() {
   super("My Exception");
 }

} class YourException extends Exception {

 YourException() {
   super("Your Exception");
 }

} class LostException {

 public static void main(String[] args) {
   try {
     someMethod1();
   } catch (MyException e) {
     System.out.println(e.getMessage());
   } catch (YourException e) {
     System.out.println(e.getMessage());
   }
 }
 static void someMethod1() throws MyException, YourException {
   try {
     someMethod2();
   } finally {
     throw new MyException();
   }
 }
 static void someMethod2() throws YourException {
   throw new YourException();
 }

}</source>

catch divide-by-zero error

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
   int d, a;
   try {
     d = 0;
     a = 42 / d;
     System.out.println("This will not be printed.");
   } catch (ArithmeticException e) { // 
     System.out.println("Division by zero.");
   }
   System.out.println("After catch statement.");
 }

}</source>

Demonstrate multiple catch statements.

   <source lang="java">

class MultiCatch {

 public static void main(String args[]) {
   try {
     int a = args.length;
     System.out.println("a = " + a);
     int b = 42 / a;
     int c[] = { 1 };
     c[42] = 99;
   } catch (ArithmeticException e) {
     System.out.println("Divide by 0: " + e);
   } catch (ArrayIndexOutOfBoundsException e) {
     System.out.println("Array index oob: " + e);
   }
   System.out.println("After try/catch blocks.");
 }

}</source>

Handle an exception and move on.

   <source lang="java">

import java.util.Random; public class MainClass {

 public static void main(String args[]) {
   int a = 0, b = 0, c = 0;
   Random r = new Random();
   for (int i = 0; i < 32000; i++) {
     try {
       b = r.nextInt();
       c = r.nextInt();
       a = 12345 / (b / c);
     } catch (ArithmeticException e) {
       System.out.println("Division by zero.");
       a = 0; // set a to zero and continue
     }
     System.out.println("a: " + a);
   }
 }

}</source>

Try statements can be implicitly nested via calls to methods

   <source lang="java">

class MethNestTry {

 static void nesttry(int a) {
   try {
     if (a == 1)
       a = a / (a - a);
     if (a == 2) {
       int c[] = { 1 };
       c[42] = 99; // generate an out-of-bounds exception
     }
   } catch (ArrayIndexOutOfBoundsException e) {
     System.out.println("Array index out-of-bounds: " + e);
   }
 }
 public static void main(String args[]) {
   try {
     int a = args.length;
     int b = 42 / a;
     System.out.println("a = " + a);
     nesttry(a);
   } catch (ArithmeticException e) {
     System.out.println("Divide by 0: " + e);
   }
 }

}</source>