Programming with Result Codes

Use result codes (also called error codes) to indicate minor errors and issue warnings. A result code can be a simple Boolean value (typically, true indicates success, false indicates an error), or it can be a numeric value. The following code shows a setSize method that returns an integer as a result code.

// (Optional) Declare symbolic constants to represent code values.
public final int TOO_SMALL = -1;
public final int OK = 0;
public final int TOO_BIG = 1;

...

public int setSize(int newSize) {
  if (newSize < 15) return TOO_SMALL;
  if (newSize > 37) return TOO_BIG;
  mSize = newSize;
  return OK;
}    

Code that calls setSize should test the return value to check for errors. For example,

public void grow(int amount) {
  int result = setSize(amount);
  String msg = "";
  switch (result) {
    case TOO_SMALL : 
      msg = "New size is too small.";
      break;
    case TOO_BIG:
      msg = "New size is too big.";
      break;
    case OK : 
      msg = "New size is OK.";
      break;
  }
  System.out.println(msg);
}