Java 天地·Core Java·Lecture Notes·Unitt4 - Control of execution

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Content Page # 17

Layout convention: placement of braces "{" "}" for compound statements

There are a number of conventions for the layout of the braces of compound statements. Although most people agree that it is easier to read a program when the open and corresponding close braces are lined up vertically (i.e. tabbed to the same degree), such an arrangement means that the code is longer. More lines of code mean that less fits on to a screen, and the longer a piece of code, the harder it is to understand.

Since for this module you'll be writing relatively short programs, we will recommend you follow the convention of having the open and close brace for a compound statement aligned vertically, and on a separate line of their own. When you move on to writing very large programs, you may wish to adopt a different brace layout convention.

Consider this loop statement from one of the bouncing ball applications investigated in unit 2:

for( int i = 0; i < balls.length; i++){
balls[i].paint( g );
balls[i].move();}
rBall.paint( g );
rBall.move();

In fact, due to the indentation convention followed, it is reasonably clear which statements are to be repeated in the loop. However, we can make it even clearer that there is a compound statement, and that the open and close braces are both present, by placing the braces on their own lines:

for( int i = 0; i < balls.length; i++)
{
    balls[i].paint( g );
    balls[i].move();
}
    rBall.paint( g );
    rBall.move();

You should layout the compound statement of all iteration statements, selection statements, and other compound statements in a similar way. Another example of this convention, this time of with an ifstatement, is as follows:

if( invalidPINEntered )
{
disp("Error: Personal Identity Number
not recognised-transaction cancelled");
cancelTransaction();
}
else
{
displayMessage("Personal Identity Number confirmed");
processTransaction();
}

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