Nothing is being output to the console! (Java, Eclipse Mars)

Question

So basically I am experimenting with writing a path finding program that find a path from some point in a 10*10 grid to another, that is fine.

I have a class Path that is an ArrayList of GridSquares (which are just glorified co-ordinates).

I have written a small method within the Path class to display the path, and this is where the problem, which is so minor but so very infuriating, arises.

When I try to run the code, and call displayPath, nothing is output to the console and the program terminates with no errors.

Here is the code for displayPath:

public void displayPath(){
    System.out.println("This is displayPrint"); //This line is included to make sure the program calls the method correctly.
    for(int i=1; i==10; i++){
        for(int j=1; j==10; j++){
            if(this.includesSquare(i, j)){
                System.out.print("[x]");
            } else {
                System.out.print("[ ]");
            }
        }
        System.out.print("\n");
    }
}

I included the first line to ensure that the console/System.out.print() was working correctly and this gets displayed every time the method is called.

Here is the code for includesSquare:

public boolean includesSquare(int x, int y){
    for(GridSquare square : this.path){
        if(square.getX()==x && square.getY()==y){
            return true;
        }
    }
    return false;
}

I have uninstalled and re-installed Eclipse, copied the java files into a new project ect and nothing seems to make any difference. I know the console is working fine as it displays the first line of displayPath correctly.

Any help is greatly appreciated!

Is this: `\\This line is included [...]` part of your code? Because you comment with forward slashes, not backslashes. — CubeJockey, Oct 01 '15 at 19:54
What is your intent with `for(int i=1; i==10; i++)` ? Specifically the `i == 10` condition — CubeJockey, Oct 01 '15 at 19:55
basically I want the loop to finish when i or j==10, is this not possible with a for loop, I was not aware! — , Oct 01 '15 at 19:58
change the condition to `j<=10`.With your code you are saying that execute the loop only if `j=10` and nothing else — singhakash, Oct 01 '15 at 19:59
You can, but instead that condition is moreso used to express when you want the loop to keep running. When you initialize `i` to 1, it won't be `==` to 10, and so the loop doesn't run even once :). Instead you want `i < 10` so that your loop runs as long as `i` is less than 10. And as you say, it will terminate when i == 10. — CubeJockey, Oct 01 '15 at 19:59
Wow you uninstalled and re-installed? Come on the site and let us look it over before going as extreme as uninstalling/installing. :) We are here to help. — gonzo, Oct 01 '15 at 20:00
it is an easy fix, can be replaces with i<11 but i didn't see the issue with using == as they both resolve to a Boolean anyway. Ahhh @Trobbins that makes sense! — , Oct 01 '15 at 20:00
yeah! @gonzo i read elsewhere that people with a similar problem had managed to solve by reinstalling! :P — , Oct 01 '15 at 20:03

gla3dr · Accepted Answer · 2015-10-01T22:07:53.763

3

for(int i=1; i==10; i++) and for(int j=1; j==10; j++) will not work.

The middle condition (i==10) is supposed to say when the loop is supposed to be executed. As it is, you are saying you only want the loop to execute when i is equal to 10. Since i is initially equal to 1, it will skip right over the loop.

What you will likely want is

for(int i=1; i<10; i++)

This way, when i is equal to 1, it satisfies the condition that it is less than 10, so the loop will get executed and i will increment. This will keep happening until i is equal to 10, at which point the condition i<10 fails, so the loop will exit.

In less words, you want your condition to say "loop while this is true" as opposed to "loop until this is true".

edited Oct 01 '15 at 22:07

answered Oct 01 '15 at 19:54

gla3dr

2,179
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Was gonna edit that in after. Patience @MarounMaroun! :P – gla3dr Oct 01 '15 at 19:55
3

@gla3dr you're allowed to wait until your answer is complete before posting your answer. – CubeJockey Oct 01 '15 at 19:56
They won't work because if `i=1`, then `i==10` is false, and the loop will terminate. Please add an explanation to your answer. – Maroun Oct 01 '15 at 19:59
@gla3dr Thanks! for some reason i was thinking about the middle statement as a sort of 'go until this' statement which doesn't actually make a whole lot of sense, but id just never thought about it before! – Oct 01 '15 at 20:05
@Trobbins When you say I am allowed to, do you mean I should? – gla3dr Oct 01 '15 at 21:53

score 1 · Answer 2 · answered Oct 01 '15 at 20:00

for(int i=1; i==10; i++){ is where your problem lies.

The syntax for the for loop is as follows:

for(<initial condition>; <checking condition>; <incrementing>)

So what you have is

Staring from i = 1, increment by 1 while i == 10. Well since i starts at 1, you've already failed at the first step!

Turn your for loop into while loop to understand this better:

int i = 1;
while(i == 10) {
    doSomething();
    i++;
}

So of course that won't work.

Nothing is being output to the console! (Java, Eclipse Mars)

2 Answers2