Loops and Logic - Beginning Java 2 SDK - page 81

Try It Out - Deciphering Characters the Easy Way
Replace the outer if - else loop and its contents in LetterCheck.java with the following:
if(symbol >= 'A' && symbol <= 'Z') { // Is it a capital letter
System.out.println("You have the capital letter " + symbol);
} else {
if(symbol >= 'a' && symbol <= 'z') { // or is it a small letter?
System.out.println("You have the small letter " + symbol);
} else { // It is not less than z
System.out.println("The code is not a letter");
}
}
How It Works
Using the && operator has condensed the example down quite a bit. We now can do the job with two
if s, and it's certainly easier to follow what's happening.
You might want to note that when the statement in an else clause is another if , the if is sometimes
written on the same line as the else , as in:
if(symbol >= 'A' && symbol <= 'Z') { // Is it a capital letter
System.out.println("You have the capital letter " + symbol);
} else if(symbol >= 'a' && symbol <= 'z') { // or is it a small letter?
System.out.println("You have the small letter " + symbol);
} else { // It is not less than z
System.out.println("The code is not a letter");
}
I think the original is clearer, so I prefer not to do this.
&& versus &
So what distinguishes && from & ? The difference between them is that the conditional && will not bother to
evaluate the right-hand operand if the left-hand operand is false , since the result is already determined in
this case to be false . This can make the code a bit faster when the left-hand operand is false .
For example, consider the following statements:
int number = 50;
if(number<40 && (3*number - 27)>100) {
System.out.println("number = " + number);
}
Here the expression (3*number - 27)>100 will never be executed since the expression number<40
is always false . On the other hand, if you write the statements as: