Download Java Programming: Understanding Control Structures and Conditional Statements and more Study notes Electrical and Electronics Engineering in PDF only on Docsity!
Introduction to Programming
with Java, for Beginners Control Structures
ESE
1/
Sequential Control Flow
Consists of just a list of commands to be donein order
Welcome to Dr. Java> int num = 2;> int sqNum;> sqNum = num * num;> System.out.println(sqNum); //Or just type:sqNum 2
ESE
2/
What are control Structures?
Limitations of sequential control flow
Cannot choose whether or not to perform acommand/instruction
Cannot perform the same command morethan once
Such programs are extremely limited!
Control structures
allow a program to
base its behavior on certain conditions
ESE
3/
Recap: Boolean
Boolean
is one of the eight primitive types
Only 2 value: true, or false
Booleans
are used to make yes or no decisions
All control structures use Booleans
The following expression each give a
Boolean
result:
(12 == 13) //results to
false
//results to
true
Thus based on certain conditions we can alterthe outcome or flow of the program
ESE
4/
Conditionals (“if” statements)
An “if” statement is a
flow control
statement
It is also called a
conditional
, or a branch
We’ll see several “flavors”
An “if” all by itself
An “if” with an “else” part
An “if” with an “else if” part
ESE
5/
//Assume
x
is
an
integer
if((x
System.out.println(x
is
even”);
“if” statement
If the condition is true, then the statement(s) (i.e.instructions) will be executed. Otherwise, it/they won’t.
if (condition){
statement(s)
ESE
6/
“if-else” statement
//Assume
x
is
an
integer
if((x
System.out.println(x
is
even”);
} else
System.out.println(x
is
odd”);
if (condition){
statement(s)
} else
statement(s) }
ESE
7/
Syntax & Explanation
Example
if (condition){
statement(s)
} else {
statements(s)
} If the condition is true,then the statement(s)in the “if block” areexecuted.Otherwise, if there isan “else” part, thestatement(s) in it areexecuted.
//Determine smaller of two integersnumbers & put it variable “min”int min;int x = 5;int y = 10;if (x <= y){
min = x;
} else {
min = y;
}
Example: “if-else” statement
ESE
12/
A “Loop”
A simple but powerful mechanism for “making lots ofthings happen!”
Performs a statement (or block) over & over
Usually set up to repeat an action until some condition issatisfied
Computing Scenarios Examples
Run an application until user hits “quit” button
Read characters until end of file reached
Deal card hands until game over
ESE
13/
Syntax of the
while statement
condition
is a true/false (boolean) expression
If
condition
is initially false, the statement is never
executed
If
condition
is true,
statement
is executed and
condition
is re-evaluated
The
statement
should eventually make the loop stop
while (
condition
statement(s)
ESE
14/
A
while Loop to Print Numbers
// Print the numbers 1 thru 10int x = 1;while (x <= 10){
System.out.println(x);x = x + 1;
What happens if you forget the statement x = x + 1?
We print value 1 forever
Known as
infinite
loop
ESE
15/
More
Infinite Loops
// Some infinte loops are intentionalwhile
(true){
statement(s)
} // Others are notint
x
while
(x
statement(s)
which
don’t
change
x
ESE
16/
Compute Square of first 10 numbers //In Square.java
int
num
int
sqNum
while
(num
sqNum
num
num;
System.out.println(num
" + sqNum);
num
num
ESE
17/
For Loop
for (init; end-test; re-init){
statement
Executes loop body as long as
end-test
evaluates to TRUE
Initialization and re-initializationcode included in loop statement
Note: Test is evaluated
before
executing loop
body
ESE
18/
While vs. For
Explanation
Code
An example ofa while loopthat has thispattern
int x = 1;while (x <= 10){
System.out.println(x);x = x + 1;
}
A for loopthat does thesame thing
for (int x = 1; x <= 10; x = x + 1){
System.out.println(x);
}^ Note:
For
loops are used generally for bounded iteration
ESE
19/
for (expr1; condition; expr3){
statement(s)
}
for
Syntax
Type of Loop
while (condition){
statement(s)
}
while
Summary of Loops
