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Easy Learn Java: Programming Articles, Examples and Tips - Page 405


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Java: 'if' Statement - Braces

Go to all tips in Java Notes by Fred Swartz

Java: 'if' Statement - Braces

Braces { } not required for one statement

If the true or false part of and if statement has only one statement, you do not need to use braces (also called "curly brackets").

Form

The if statement doesn't need braces if there is only one statement in a part. Here both the true and false parts have only one statement:
   if (condition) 
      one statement to do if condition is true
   else
      one statement to do if condition is false
   

Example 1 - true and false parts

Here is a paintComponent() method both with and without braces which is possible only because each clause contains only one statement.
public void paintComponent(Graphics g) {
  super.paintComponent(g);  // call parent to paint background
  if (marks < 50) {
     g.setColor(Color.red);   // bad marks in red
  }else{
     g.setColor(Color.black); // good marks in black
  }
  g.drawString("Score = " + marks, 10, 50);
}

and now without braces. Altho correct, it is not as safe a style.
public void paintComponent(Graphics g) {
  super.paintComponent(g);  // call parent to paint background
  if (marks < 50)
     g.setColor(Color.red);   // bad marks in red
  else
     g.setColor(Color.black); // good marks in black
  g.drawString("Score = " + marks, 10, 50);
}

Example 2 - only a true part

If there is only a true part of the if statement, it only needs braces if there is more than one statment.
public void paintComponent(Graphics g) {
  super.paintComponent(g); 
  if (marks < 50)
     g.setColor(Color.red);   // bad marks in red
  g.drawString("Score = " + marks, 10, 50);
}
If the if condition is false, this will not set the color, so the default color will be used (black).

Should you always use braces?

If there is one statment, many programs use braces to make the code more robust. This is a safer practice because any later addition of a statement to one of the clauses will require braces. If you don't have the braces with multiple statements, the compiler may not give any error message, but your code will not do what was expected.

What is a statement?

A statement is a part of a Java program. We have already seen some simple statements:
  • Assignment statement (eg, x = 1;).
  • Method call statement (eg, g.setColor(Color.red);).
  • if statement.
There are about ten kinds of statements. Many of them use braces for grouping statements in the same way that the if statement uses braces.
2155 bytes more | comments? | Printer Friendly Page  Send to a Friend | Score: 4.33
Posted by jalex on Friday, September 23, 2005 (00:00:00) (4692 reads)

The code in a finally clause will never fail to execute, right?

Go to all tips in Java IAQ by Peter Norvig

This tip is reprinted on JavaFAQ.nu by by courtesy of Peter Norvig I am thankful for his important contributions to my site - 21 Infrequently Answered Java Questions. Alexandre Patchine

Q: What is an Infrequently Answered Question?

A question is infrequently answered either because few people know the answer or because it is about an obscure, subtle point (but a point that may be crucial to you). I thought I had invented the term, but it also shows up at the very informative About.com Urban Legends site. There are lots of Java FAQs around, but this is the only Java IAQ. (There are a few Infrequently Asked Questions lists, including a satirical one on C.)

Q: The code in a finally clause will never fail to execute, right?

Well, hardly ever. But here's an example where the finally code will not execute, regardless of the value of the boolean choice:

  try {
    if (choice) {
      while (true) ;
    } else {
      System.exit(1);
    }
  } finally {
    code.to.cleanup();
  }



comments? | Printer Friendly Page  Send to a Friend | Score: 4.75
Posted by jalex on Thursday, September 22, 2005 (00:00:00) (2499 reads)

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