[Java] Checking if input is valid.

How can i check if input it valid, and if it isnt, request the user to put in valid information?

		studentName = JOptionPane.showInputDialog("Student Mark Calculator \n Enter Your Name:");
// Would check if the studentName contains something, if not, request again.

		temp = JOptionPane.showInputDialog("Student Mark Calculator \n Enter Your Assignment Mark (140 Max):");
		assignmentMark = Integer.parseInt(temp);
// Would check if the user entered a number. If its not a number, or nothing at all, request again.

		temp = JOptionPane.showInputDialog("Student Mark Calculator \n Enter Your Mid-Term Exam Mark (60 Max):");
		midExamMark = Integer.parseInt(temp);
// Would check if the user entered a number. If its not a number, or nothing at all, request again.

		temp = JOptionPane.showInputDialog("Student Mark Calculator \n Enter Your Final Exam Mark (85 Max):");
		fExamMark = Integer.parseInt(temp);
// Would check if the user entered a number. If its not a number, or nothing at all, request again.

Code (markup):

I know how it would be done in php (sucks learning a new language at first, lol) But with java, as soon as lets say 'Me' is entered, it crashes.

 

You might have to do something like this:

boolean boolInputOK = true;
try {
     assignmentMark = Integer.parseInt(temp);
} catch (NumberFormatException e) {       
     //System.out.println(temp + " is not a number! " + e.getMessage());
     boolInputOK = false;
}

Code (markup):

Around each int parse. Then, if boolInputOK == false at the end, get the input again.

 

always check for null values before processing the data. Or you might get a NPE.