Java class2010.10.22
Outline
• for loop
• while loop
• do while loop
• How to choose?
• Nested loop
for loop
EX:
for ( i=0 ; i<=100 ; i++ ) // 迴圈條件運算式{
// 迴圈內的動作 ;
}
迴圈內的動作迴圈內的動作
進入迴圈
true
false
離開迴圈
迴圈條件運算式
while loop EX:
int count=0;
while ( count<100 )
{
System.out.println(”Hello!”);
count++;
}
p.s count 從 0 累加到 99
loop-
continuation condition?
Statement(s)(loop body)
false
true
count=0
(count < 100) ?
System.out.println(“Hello!”);count++;
練習 :
用 for loop 以及 while loop, 寫九九乘法表 格式 :
do while loop
EX:
int count=0;
do {
System.out.println(”Hello!”);
count++;
} while ( count<100 );
loop-continuation condition?
Statement(s)(loop body)
false
true
count=0
(count < 100) ?
System.out.println(“Hello!”);count++;
Pretest & Posttest loop
• 先測迴圈 : while 、 for
The condition is checked before the loop body is excuted.
• 後測迴圈 : do while
The condition is checked after the loop body is excuted.
How to choose?
A for loop may be used if the number of repetitions is known in advance.
A while loop may be used if the number of repetitions is not fixed.
A do while loop can be used to replace a while loop if the loop body has to be executed before the condition is tested.
課本 p.152
Nested( 巢狀 ) loop
for
{
…….
for
{
…….
}
}
課本 p.153
回家看 :
p.152 ~ p.153
