How to use OR in Java If statement

You seem to be posting a code fragment, because the brackets don't match up. Plus, you don't show any code that prints an error message.

But the main point of your question seems to be about a logic problem, not a syntax error with the code. So I'll pretend the syntax errors aren't there (although you do need to fix them). The logic problem seems to be here:

if (x >= 0 || y >= 0) { // all is good } else { // print error message } 

This test will succeed if either x or y is non-negative. From your description, you want the test to fail if either is negative. For that, you need to either reverse the sense of the tests:

if (x < 0 || y < 0) { // print error message } else { // all is good } 

or else use AND instead of OR:

if (x >= 0 && y >= 0) { // all is good } else { // print error message } 

If you want both numbers to be >=0 you should use AND instead of OR. If x is -5 but y is 7, the code will execute, but your counting from 0 to -5 will be pointless.

I recommend you use else if as opposed to 2 'if's, for example

 If (x >= 0 || y >= 0){ //your code } else if (x == y) { //your code } else { //your code } 

A better way to continuously prevent the user from inputting negative numbers would be:

Scanner in = new Scanner(System.in); int x, y; do { System.out.println("Input x:"); x = in.nextInt(); System.out.println("Input y:"); y = in.nextInt(); } while (x < 0 || y < 0); 

This do-while loop will ask for inputs until both x and y are positive integers. I'm not sure if this is what you wanted to achieve but that's what I gathered from your question since you said you wanted to use an if statement to prevent negative input.

Other than that, you're missing closing curly brackets like a couple people said already, but your code snippet looks incomplete. For future reference, please include more of your code for people to work from and/or the exceptions you get when trying to run your code.