java throw nullpointerexception code example

Example 1: how to use a try catch for a null pointer exception in java

int n;//decalred as null
n = n + 1;//null pointer exception
/////////////////////////////////////
int n = 5;
n = n + 1;//no null pointer exception

Example 2: 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 3: exception is null

//Bug with VS: Exception e == null
//Happens when multiple catch variables are the same
//an example of the solution:
try
{
    // do something
}
catch (WebException webEx) // using a variable named 'webEx' for this catch
{
    Logger.Log("Error while tried to do something. Error: " + webEx.Message); // <-
}
catch (Exception ex) // using a DIFFERENT variable for this one
{
    Logger.Log("Error while tried to do something. Error: " + ex.Message);
}

Example 4: nullpointerexception java

Integer num;
num = new Integer(10);

Example 5: NullPointerException

TestObject a = new TestObject();String b = a.getTestResult();b.toString();

Example 6: nullpointerexception java

int x;
x = 10;