Jiakuang He

How To Debug - Java

Other Online IDE: Online Java Debugger - online editor (onlinegdb.com)

Practice Code

The following code doesn’t get the expected result.

You need to use the debug technique to find why it doesn’t working correctly.

Expected

Real

Challenge Code

Draw a heart shape.

The heart shape equation is:

(x^2+y^2-1)^3-x^2*y^3=0

image-20230314115942429

Use the following code and use the debug technique to find where need to fix:

class Main {
  public static void main(String[] args) {
    for (double y = 1.5; y > -1.5; y -= 0.1) {
      for (double x = -1.5; x < 1.5; x += 0.05) {
        double temp = (x * x) + (y * y) - 1;
        double value = (temp * temp * temp) - (x * x) * (y * y * y);
        if (value == 0.0)// Fix me
          System.out.print(" ");
        else
          System.out.print("❤");
      }
      System.out.println();
    }
  }
}

Answer:

class Main {
 public static void main(String[] args) {
   for (double y = 1.5; y > -1.5; y -= 0.1) {
     for (double x = -1.5; x < 1.5; x += 0.05) {
       double temp = (x * x) + (y * y) - 1;
       double value = (temp * temp * temp) - (x * x) * (y * y * y);
       if (value >= 0.0)
         System.out.print(" ");
       else
         System.out.print("❤");
     }
     System.out.println();
   }
 }
}

Expected

image-20230314120912308

Real

image-20230314120936066

Debug With Replit

  1. Find the debugger button on the left side Tools

    image-20230314121509102

  2. Create a breakpoint, click the left side of the line column.

    image-20230314121631105

  3. Click the Run button.

​ image-20230314121943993

  1. On the debugger Tab, click the blue Run button.

image-20230314121528953

On replit, you should run the programm first. Then, use the debugger.

Because replit use the command Debug (sh -c java-debug) to debug the running command.

Reference

[Desmos Graphing Calculator](https://www.desmos.com/calculator)