Conditional Output

An annoyance of debugging with print statements is:

• When you're debugging, you put the statements in your program.

• When you're done debugging, you take the extra statements out.

• If you find a problem later on, you put them back in...

• When you've fixed the problem, you take them back out...

• If you find another problem later on, you put them back in...

To fix this problem, put your debug print statements in a conditional statement.

We can use a static boolean variable to control all debugging statements.

static boolean debug = true;

  // Somewhere in the program...
  if(debug) {
    System.out.println("We got past the calculation");
  }

  // Somewhere else...
  if(debug) {
    System.out.println("value: " + amountDue);
  }

Now if we change debug to false and recompile, messages are turned off.

Another technique is to define a method for printing debug messages.

public static void debug(String msg) {
  boolean debugging = true;
  if (debugging) {
    System.out.println(msg);
  }
}

* Now we don't repeat if(debug) in our code.

// Somewhere in the program...
debug("We got past the calculation");

// Somewhere else...
debug("value: " + amountDue);

Practice Exercise

When you are new to programming, adding System.out.println() statements to find bugs in your code is fine.

However, these statements could accidentally appear in logs (text files that save output), and are considered unprofessional. There are better ways to debug.

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