user2173361 user2173361 - 5 months ago 8
Java Question

Point x value changes for no reason

I have this method for looking for a free position inside a matrix. This is the output i get when I print the

matrix
.

1 0 0 0 0 0 0
1 1 1 0 0 0 0
1 1 1 0 0 0 0
0 1 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0


I have a
currentPos
of
(0,0)
. The next free Position should be (0,1). when I call
NextFreePos()
it will change the
currentPos.x
value even though It shouldnt change. I only change the
x
if i get a true in the second for loop, but this always returns
false
, because I make
stop = true
inside the first for loop
Here is the output I get when I run this method:

NEXT POS = (0;0)
SAME X
NEXT POS = (1;1) // I dont get why the x (first value) changed to 1

public void nextFreePos(Point currentPos){
// display the OLD POS (x,y) <-- x = row and y = column
System.out.println("OLD POS = ("+(currentPos.x)+";"+currentPos.y+")");
boolean stop = false;
// check if there is a free Pos in current row, starting from current y
for(int y = currentPos.y; y < 7; y++){
// check if Position is free and no free position has been found yet
if(matrix[currentPos.x][y] == 0 && stop == false){
stop = true;
System.out.println("SAME X");
currentPos.y = y;
}
}
currentPos.x++;
for(int x = currentPos.x; x < 7; x++){
for(int y = 0; y < 7; y++){
// check if Position is free and no free position has been found yet
if(matrix[x][y] == 0 && stop == false){
stop = true;
System.out.println("OTHER X");
// set the position to x and y
currentPos.x = x;
currentPos.y = y;
}
}
}
// display the NEXT POS (x,y)
System.out.println("NEXT POS = ("+currentPos.x+";"+currentPos.y+")");
}

Answer

See the highlighted piece of code.

NEXT POS = (0;0)
SAME X
NEXT POS = (1;1) // I dont get why the x (first value) changed to 1

 public void nextFreePos(Point currentPos){
        // display the OLD POS (x,y) <-- x = row and y = column
        System.out.println("OLD POS = ("+(currentPos.x)+";"+currentPos.y+")");       
        boolean stop = false;
        // check if there is a free Pos in current row, starting from current y
        for(int y = currentPos.y; y < 7; y++){
            // check if Position is free and no free position has been found yet
            if(matrix[currentPos.x][y] == 0 && stop == false){
                stop = true;
                System.out.println("SAME X");
                currentPos.y = y;
            }
        }        
        currentPos.x++;
        for(int x = currentPos.x; x < 7; x++){
            for(int y = 0; y < 7; y++){
                // check if Position is free and no free position has been found yet
                if(matrix[x][y] == 0 && stop == false){
                    stop = true;
                    System.out.println("OTHER X");
                    // set the position to x and y
                    currentPos.x = x;
                    currentPos.y = y;  
                }                
            }
        }  
        // display the NEXT POS (x,y)
        System.out.println("NEXT POS = ("+currentPos.x+";"+currentPos.y+")");       
    }
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