Java throw statement

Example: Normally built-in exceptions are thrown by the JVM but user can also create and throw any exception although this is normally not done. The throw statement is needed for throwing user-defined exceptions, which is discussed in a later section.

The following program creates and throws an exception

class ThrowDemo {

static void demoproc() {

try {

int c = 0, a = 0;

if (a == 0)

int b = c / a;

} catch (ArithmeticException e) {

System.out.println("Caught inside demporoc.");

throw e;

}

throw new ArithmeticException("Division by zero");

}

public static void main(String args[]) {

try {

demoproc();

} catch (ArithmeticException e) {

System.out.println("Recaught: " + e);

}

}

}

Output:

Caught inside demporoc.

Recaught: java.lang.ArithmeticException: Division by zero

Example: The following example demonstrates that if a checked-exception is thrown using throw statement then it must either be caught or declared in the throws clause.

import java.io.*;

class ThrowsDemo {

static void throwOne() throws IOException {

System.out.println("inside throwOne");

throw new IOException("Demo");

}

public static void main(String args[]) {

}

}

Output: above program will not compile and result in following compile time error.

throwOne();

Example: The above example is re-written such that the method throwOne() is called in a try block.

import java.io.*;

class ThrowsDemo

{ static void throwOne() throws IOException

{ System.out.println("inside throwOne");

}

public static void main(String args[])

{ try

throw new IOException("Demo");

{ throwOne();

}

catch(IOException e)

{ e.printStackTrace();

}

}

}

Output: results in an exception at run-time.