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if (booleanExpression)
{
statement(s);
}
Example:
if ((i >= 0) && (i <= 10))
{
System.out.println("i is an “ +
“integer between 0 and 10");
}
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if (booleanExpression)
{
statement(s)-for-the-true-case;
}
else
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statement(s)-for-the-false-case;
}
if...else Example
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if (radius >= 0)
{
area = radius*radius*PI;
System.out.println("The area for the “
+ “circle of radius " + radius +
" is " + area);
}
else
{
System.out.println("Negative input");
}
If…Else?
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switch?
3* if?
P¨V ?
P??? 4 b Java4
switch? μr1) ? ×Hq b?E1
switch (switch-expression)
{
case value1: statement(s)1;
break;
case value2: statement(s)2;
break;
……
case valueN: statement(s)N;
break;
default: statement(s)-for-default;
}
switch?
3* if?
P¨V ?
P??? 4 b Java4
switch? μr1) ? ×Hq b?E1
switch (switch-expression)
{
case value1: statement(s)1;
break;
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break;
……
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break;
default: statement(s)-for-default;
}
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case value1: statement(s)1;
break;
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……
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break;
default: statement(s)-for-default;
}
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break;
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switch (year)
{
case 7: annualInterestRate = 7.25;
break;
case 15: annualInterestRate = 8.50;
break;
case 30: annualInterestRate = 9.0;
break;
default: System.out.println(
"Wrong number of years, enter 7, 15, or
30");
}
switch?
@m
numOfYears
annulInterestRate
=7.25
/BH?
7
default
System.out.println
(“Wrong number
of years”);
annulInterestRate
=8.50
annulInterestRate
=9.0
15 30
3.2.5 HqVr
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variable = booleanExpression ?
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if (x > 0) y = 1
else y = -1;
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while (continue-condition)
{
// loop-body;
}
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TestWhile
while?ì
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false
true
Statement(s)
Next Statement
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3.3.2 do?ì
do?ì
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// Loop body;
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3.3.3 for?ì
for (?ìM
S? ?ìHq ??? )
{
//loop body;
}
Example:
int i;
for (i = 0; i<100; i++)
{
System.out.println("Welcome to Java!” + i);
}
for?ì
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TestSum Run Class
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TestMulTable Run Class
3.4
P¨1o3 break
false
true
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break
3.5
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false
true
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k break?
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TestBreak
Run Class
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TestContinue Run Class
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￥? -Y} b
outer:
for (int i=1; i<10; i++)
{
inner:
for (int j=1; j<10; j++)
{
if (i*j > 50)
break outer;
System.out.println(i*j);
}
}
?T| break outerD? break
5 ??3?$
3.6
L èD
) Example 3.7 9
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r-
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5000
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5000
?í ~10000
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10001
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12%
FindSalesAmount Run Class
3.6
L èD
) Example 3.8 A
U
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{
1
212
32123
4321234
543212345
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Run Class
3.6
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) Example 3.9 A
U
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U - 50?
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v? 1￥?
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PrimeNumber
Run Class
ˉ 5
) 3.1 /
}
? ?μ
{·
{2T
x = 2;
y = 3;
if (x > 2)
if (y > 2)
{
int z = x + y;
System.out.println(“z is ” + z);
}
else
System.out.println(“x is ” + x);
ˉ 5
) 3.2 /
}
? ?μ
{·
{2T
x = 3;
y = 2;
if (x > 2)
{
if (y > 2)
{
int z = x + y;
System.out.println(“z is ” + z);
}
}
else
System.out.println(“x is ” + x);
ˉ 5
) 3.3 V[ü switch?yD??N￥ if?
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V ? V[
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switch? a y
^
$
x = 3;
switch (x + 3)
{
case 6 y = 1;
default: y += 1;
}
ˉ 5
)3.6 3?/
? a y
^
$
x = 0;
Y = (x > 0) ? 1 : -1;
)3.7 /
?ì8×ˉ
Q$?ì
{
I
1$
int i = 1;
while (i < 10)
if (( i++ )%2 == 0)
System.out.println(i);
ˉ 5
) 3.8 while?ì? do?ì￥ uY
^
I
1$
) 3.9 /
?
H? ¤?￥ sum′M]
?$
for
int i = 0 i < 10; ++i
{
sum += i;
}
for
int i = 0 i < 10; i++
{
sum += i;
}
ˉ 5
) 3.10 1o3 break￥T¨
^
I
1$/
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2
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int balance = 1000;
while (true)
{
if (balance < 9)
break;
balance = balance - 9;
}
System.out.println(“balance is ” + balance);
ˉ 5
) 3.11 1o3 continue￥T¨
^
I
1$/
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?
?$ ? ?ó
{2T b
int balance = 1000;
while (true)
{
if (balance < 9)
continue;
balance = balance - 9;
}
System.out.println(“balance is ” + balance);
I?
) 3.1 B? 3*￥ for?ìu?/
m?
) 3.2 ¨ while?ì p n
2
v? 12000￥Kl
? n b
1
12
123
1234
12345
public class Exercise3_2
{
// Main method
public static void main(String[] args)
{
int i = 1;
while (i*i <= 12000 )
{
i++;
}
System.out.println("This number is "+i);
}
}
I?
