Java Tutorial/Statement Control/try catch

An example of nested try statements.

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);
    }
  }
}

Catch different Exception types

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();
  }
}

catch divide-by-zero error

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.");
  }
}

Demonstrate multiple catch statements.

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.");
  }
}

Handle an exception and move on.

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);
    }
  }
}

Try statements can be implicitly nested via calls to methods

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);
    }
  }
}