What are the cases in which it is better to use unconditional AND (& instead of &&)

Question

I\'d like to know some cases in Java (or more generally: in programming) when it is preferred in boolean expressions to use the unconditional AND (&

Answer 1

Input validation is one possible case. You typically want to report all the errors in a form to the user in a single pass instead of stopping after the first one and forcing them to click submit repeatedly and only get a single error each time:

public boolean validateField(string userInput, string paramName) {
   bool valid;
   //do validation 

   if (valid) {
       //updates UI to remove error indicator (if present)
       reportValid(paramName);   
   } else {
       //updates UI to indicate a problem (color change, error icon, etc) 
       reportInvalid(paramName);  
   }      
}

public boolean validateAllInput(...) {

   boolean valid = true;
   valid = valid & validateField(userInput1, paramName1);
   valid = valid & validateField(userInput2, paramName2);
   valid = valid & validateField(userInput3, paramName3);
   valid = valid & validateField(userInput4, paramName4);
   valid = valid & validateField(userInput5, paramName5);

   return valid;
}

public void onSubmit() {

   if (validateAllInput(...)) {
       //go to next page of wizard, update database, etc
       processUserInput(userInput1, userInput2, ... );
   } 

}

public void onInput1Changed() {
   validateField(input1.Text, paramName1);
}


public void onInput2Changed() {
   validateField(input2.Text, paramName2);
}

...

Granted, you could trivially avoid the need for short circuit evaluation in validateAllInput() by refactoring the if (valid) { reportValid() ... logic outside of validateField(); but then you'd need to call the extracted code every time validateField() was called; at a minimum adding 10 extra lines for method calls. As always it's a case of which tradeoff's work best for you.