in java how to throw exception from function

1public static void foo() throws IOException {
2    // some code here, when something goes wrong, you might do:
3    throw new IOException("error message");
4}
5
6public static void main(String[] args) {
7    try {
8        foo();
9    } catch (IOException e) {
10        System.out.println(e.getMessage());
11    }
12}

1public void doChangePin(int oldPin, int pin) throws Exception {	//need to add throws followed by exception name
2		if (oldPin == pinCode) {
3			pinCode = pin;
4		} else {
5			throw new Exception("some message");	//throwing the exception by creating its new object
6		}
7	}

1throw new java.lang.Error("this is very bad");
2throw new java.lang.RuntimeException("this is not quite as bad");

1public static void main(String[] args) {
2	Scanner kb = new Scanner(System.in);
3    System.out.println("Enter a number");
4    try {
5    	double nb1 = kb.nextDouble();
6    	if(nb1<0)
7        	throw new ArithmeticException();
8        else System.out.println( "result : " + Math.sqrt(nb1) );
9    } catch (ArithmeticException e) {
10        System.out.println("You tried an impossible sqrt");
11    }
12}