Control Statements in Java

Presented By
Niloy Saha
Control Statements in Java
Department of Computer Science & Engineering

Control Statements
Selection
Iteration
Jump
Outlines
2

Selection
Selection Statements
Switch Statement
 Selection Statements are also called Decision Making Statements.
Selection Statements
3

if Statements
Simple if
if else
if- else- if Ladder
Nested if
if Statements
4

Simple if
Syntax :
if (condition)
{
statement1;
}
Purpose: The statements will be evaluated if the value of the condition is true.
5

Simple if
Start
End
Condition
Statements
FalseTrue
Flow Chart:
6

if else
Syntax :
if (condition)
{
statement1;
}
else
{
statement2;
}
Purpose: The statement 1 is evaluated if the value of the condition is true otherwise
statement 2 is true.
8

if else
FalseTrue
Flow Chart: Start
End
Condition
Statement 1 Statement 2
9

If-else-if Ladder
Syntax :
if(condition)
statements;
else if(condition)
statements;
else if(condition)
statements;
...
...
else
statements;
11

Examples
import java.util.Scanner;
class Day
{
public static void main(String args[])
{
Scanner s = new Scanner(System.in);
System.out.println("Enet day between 0 to 6 Day = ");
int day = s.nextInt();
if (day == 0)
{
System.out.println("n Sunday");
}
else if (day == 1)
{
System.out.println("n Monday");
}
else if (day == 2)
{
System.out.println("n Tuesday");
}
else if (day == 3)
{
System.out.println("n Wednesday");
}
else if (day == 4)
{
System.out.println("n Thursday");
}
else if (day == 5)
{
System.out.println("n Friday");
}
else
{
System.out.println("n Saturday");
}
}
}
12

Nested if
• A nested if is an if statement that is the target of another if or else.
• Nested ifs are very common in programming.
Syntax :
if(condition)
{
if(condition)
statements....
else
statements....
}
else
{
if(condition)
statements....
else
statements....
}
13

switch
Syntax :
switch (expression)
{
case value 1 :
statement 1 ; break;
case value 2 :
statement 2 ; break;
...
...
case value N :
statement N ; break;
default :
statements ; break;
}
Purpose: The statements N will be evaluated if the value of the logical expression is true.
15

switch
Flow Chart:
Case A
Case B
…
default
False
False
False
Case A Statements
break;
Case B Statements
break;
Case C Statements
break;
Default Statements
Start
Variable or Expression
True
True
True
End
16

Iteration Statements
Iterations/ Loops
while
do while
for
Each loop has four types of
statements :
 Initialization
 Condition checking
 Execution
 Increment / Decrement
18

while
Syntax:
initialization
while(final value)
{
statements;
increment/decrement;
}
Purpose: To evaluate the statements from initial value to final value with given
increment/decrement.
m=1
while(m<=20)
{
System.out.println(m);
m=m+1;
}
19

Example
class while1
{
{
int i=1;
while(i<=10)
{
System.out.println("n" + i);
i++;
}
}
}
Output :
1
2
3
4
5
6
7
8
9
10
 print values from 1 to 10
20

do while
Syntax:
initialization
do
{
statements;
increment/decrement;
}
while(final value);
m=1
do
{
m=m+1;
}
while(m==20);
21

Example
class dowhile1
{
{
int i = 1;
int sum = 0;
do
{
sum = sum + i;
i++;
}while (i<=10);
System.out.println("nntThe sum of 1 to 10 is .. " + sum);
}
}
Output :
The sum of 1 to 10 is .. 55 22

for
Syntax:
for(initialization;final value;increment/decrement)
{
statements;
}
for(m=1;m<=20;m=m+1)
{
}
23

Example
class for1
{
{
int i;
for (i=0;i<5;i++)
{
System.out.println("nExample of for loop ");
}
}
Output :
Example of for loop
Example of for loop
Example of for loop
Example of for loop
Example of for loop
24

Jump Statements
Jump
break
continue
return
25

The break statement
 This statement is used to jump out of a loop.
 Break statement was previously used in switch – case statements.
 On encountering a break statement within a loop, the execution continues with the next
statement outside the loop.
 The remaining statements which are after the break and within the loop are skipped.
 Break statement can also be used with the label of a statement.
 A statement can be labeled as follows.
statementName : SomeJavaStatement
 When we use break statement along with label as,
break statementName;
26

Example
class break1
{
{
int i = 1;
while (i<=10)
{
i++;
if (i==5)
{
break;
}
}
}
}
Output :
1
2
3
4
27

continue Statement
 This statement is used only within looping statements.
 When the continue statement is encountered, the next iteration starts.
 The remaining statements in the loop are skipped. The execution starts from the
top of loop again.
28

Example
class continue1
{
{
for (int i=1; i<1=0; i++)
{
if (i%2 == 0)
continue;
}
}
}
Output :
1
3
5
7
9
29

The return Statement
 The last control statement is return. The return statement is used to
explicitly return from a method.
 That is, it causes program control to transfer back to the caller of the
method.
 The return statement immediately terminates the method in which it is
executed.
30

Example
class Return1
{
{
boolean t = true;
System.out.println("Before the return.");
if(t)
return; // return to caller
System.out.println("This won't execute.");
}
}
Output :
Before the return.
31

Control Statements in Java

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