throw and throws in java code example

Example 1: in java how to throw exception from function

public void doChangePin(int oldPin, int pin) throws Exception {	//need to add throws followed by exception name
		if (oldPin == pinCode) {
			pinCode = pin;
		} else {
			throw new Exception("some message");	//throwing the exception by creating its new object
		}
	}

Example 2: java how to throw exception

public class ThrowException{
  public static void main(String [] args) throws Exception{ 
    //throws Exception line is needed if not using try-catch block
    throw new Exception("Errmessage");
  }
}

Example 3: java throw an exception

public static void main(String[] args) {
	Scanner kb = new Scanner(System.in);
    System.out.println("Enter a number");
    try {
    	double nb1 = kb.nextDouble();
    	if(nb1<0)
        	throw new ArithmeticException();
        else System.out.println( "result : " + Math.sqrt(nb1) );
    } catch (ArithmeticException e) {
        System.out.println("You tried an impossible sqrt");
    }
}

Example 4: java throws exception on method

static void testMethod() throws Exception {
    String test = null;
    test.toString();
}

Example 5: throw error java

throw new java.lang.Error("this is very bad");
throw new java.lang.RuntimeException("this is not quite as bad");

Example 6: throw keyword in java

Generally JVM throws the exception and
we handle the exceptions by 
using try catch block. But there are
situations where we have to throw 
userdefined exceptions or runtime exceptions.
  In such case we use throw keyword 
to throw exception explicitly.

  Syntax : throw throwableInstance;