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Control. Conditionals...Loops Comments...Constants. The simple case if() single_statement;. OR if() { statements; }. Conditionals. This can be dangerous!!!. The Classic Killer Error. if(); { statement; statement; }. Conditionals. - PowerPoint PPT Presentation
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Control
Conditionals...Loops
Comments...Constants
Conditionals
• The simple case
if(<boolean_value>)
single_statement;
This can bedangerous!!!
This can bedangerous!!!
• OR
if(<boolean_value>)
{
statements;
}
The Classic Killer Error
if(<some_boolean>);
{
statement;
statement;
}
Conditionals
• Adding the else part:
if(<boolean condition>)
{
statement;
statement;
}
else
{
statement;
statement;
}
Example:
if( leapYear ) {
febDays = 29;}else{
febDays = 28;}
Example:
if( leapYear ) {
febDays = 29;}else{
febDays = 28;}
Conditionals
• Adding the else part:
if(<boolean condition>) {
statement;
statement;
} else {
statement;
statement;
}
Example:
if( leapYear ) {febDays = 29;
} else {febDays = 28;
}
Example:
if( leapYear ) {febDays = 29;
} else {febDays = 28;
}
Loops -- Sentinel
• Pseudocode
total, i isoftype Num
total <- 0
i <- 1
loop
exitif(i > 10)
total <- total + i
i <- i + 1
endloop
• Java
int total, i;
total = 0;
i = 0;
while(i <= 10)
{
total = total + i;
i = i + 1;
}
Loops -- Test Last
• Pseudocode
total, i isoftype Num
total <- 0
i <- 1
loop
total <- total + i
i <- i + 1
exitif(i > 10)
endloop
• Java
int total, i;
total = 0;
i = 1;
do
{
total = total + i;
i = i + 1;
} while(i < 10);
for Loops
for(<init>; <while_boolean>; <inc><inc>)
statement;
• <init> is done before entering loop• <while_boolean> is checked before entering and before each subsequent iteration and must be true
• <inc><inc> is performed at the end of each iteration.
• Note: <init> and <inc><inc> can be multiple statements but for now don’t do it!
Loops -- Convenience!
• Classic while loop
int total = 0;
int i = 0;
while(i < 10)
{
total = total + 1;total = total + 1;
i = i + 1i = i + 1;
}
• for loop
int total = 0;
int i;
for(i = 0; i < 10; i++i++)
{
total = total + 1;total = total + 1;
}
Loops Summarized
while(<boolean>){statement(s);
}
do{statement(s);
} while(<boolean>);
for(<init>; <while_boolean>; <inc>){statement(s);
}
Shorthand Operators• iCounter = iCounter + 1; OR iCounter++;• iCounter = iCounter - 1; OR iCounter--;• iCounter = iCounter + 2; OR iCounter += 2;• iCounter = iCounter * 5; OR iCounter *= 5;
Last two examples: it’s “op” then “equals” (e.g., +=2), not “equals” then “op” (e.g., isn’t =+2)
• These work with +, -, *, / plus others.
• i++; // means increment i• i += 2; // means add 2 to the value of i
• WARNING: THESE ARE NOT JUST CUTE TRICKS THEY ARE VERY POWERFUL AND CAN BE MISUSED. HANDLE WITH CARE!!!
Documentation & Comments
• Two ways to do it:
// Double slashes comment out everything until the
// end of the line
/* Starts a comment which may extend multiple lines and eventually be terminated by */
Constants
• Pseudocode<CONST_ID> is <constant value>
MIN_PASSING is 60
PI is 3.14159
• Javapublic final static <type> <IDer> = <value>;
public final static int MIN_PASSING = 60;
public final static float PI = (float) 3.14159;
• Details on “why this syntax” to come soon...
