Control structures in java

 The control statement are used to control the flow of
execution of the program.
 This execution order depends on the supplied data values
and the conditional logic.
 In java program, control structure is can divide in three
parts:
1. Selection statement
2. Iteration statement
3. Jumps in statement

• Selection statement is also called as Decision making
statements.
• Because it provides the decision making capabilities to the
statements.
• In selection statement, there are two types:
1. if statement
2. Switch statement.

• The Java if statement is used to test the condition.
• It checks Boolean condition: true or false.
• There are various types of if statement in java.
1. if statement
2. if-else statement
3. Nested if-else statement
4. if-else-if ladder

• The Java if statement tests the condition.
• It executes the if block if condition is true.
Syntax:
if(condition)
{
//code to be executed
}

Example:
public class IfExample
{
public static void main(String[] arg)
{
int age=20;
if(age>18)
{
System.out.print("Age is greater than 18");
}
}}
Output: Age is greater than 18

• The Java if-else statement also tests the condition.
• It executes the if block if condition is true otherwise else
block is executed.
Syntax:
if(condition)
{
//code if condition is true
}
Else
{
//code if condition is false
}

public class IfElseExample
{
public static void main(String[] args)
{
int number=13;
if(number%2==0)
{
System.out.println("even number");
}
Else
{
System.out.println("odd number");
} }}
Output: odd number

• The Nested if-else statement executes one if or else if
statement inside another if or else if statement.
Syntax:
if(Boolean_expression 1)
{
// Executes when the Boolean expression 1 is true
if(Boolean_expression 2)
{
// Executes when the Boolean expression 2 is true
}
}

public class Test
{
public static void main(String args[])
{
int x = 30;
int y = 10;
if( x == 30 )
{
if( y == 10 )
{
System.out.print("X = 30 and Y = 10");
}
}}}

• The if-else-if ladder statement executes one condition from multiple
statements.
Syntax:
if(condition1)
{
//code to be executed if condition1 is true
}
else if(condition2)
{
}
else if(condition3)
{
}
...
Else
{
//code to be executed if all the conditions are false
}

public class IfElseIfExample
{
{
int marks=65;
if(marks<50)
{
System.out.println("fail");
}
else if(marks>=50 && marks<60)
{
System.out.println("D grade");
}
{
System.out.println("C grade");
}
{
System.out.println("B grade");
}
{
System.out.println("A grade");
}
{
System.out.println("A+ grade");
}
else
{
System.out.println("Invalid!");
}}}
Output: C grade

• The Java switch statement executes one statement from
multiple conditions.
• It is like if-else-if ladder statement.
Syntax:
switch(expression)
{
case value1:
//code to be executed;
break; //optional
case value2:
//code to be executed;
break; //optional
......
default:
code to be executed if all cases are not matched;
}

public class SwitchExample
{
{
int number=20;
switch(number)
{
case 10: System.out.println("10");break;
default:System.out.println("Not in 10, 20 or 30");
}}}
Output: 20

• Looping is also called as iterations.
• The process of repeatedly executing a statements and is
called as looping.
• The statements may be executed multiple times.
• If a loop executing continuous then it is called as Infinite
loop.
• In Iteration statement, there are three types of operation:
1. for loop
2. while loop
3. do-while loop

• The simple for loop is same as C/C++.
• We can initialize variable, check condition
and increment/decrement value.
Syntax:
for(initialization;condition;incr/decr)
{
}

public class ForExample
{
{
for(int i=1;i<=10;i++)
{
System.out.print(i);
}
}
}
Output:
12345678910

• The Java while loop is used to iterate a part of the program
several times.
• If the number of iteration is not fixed, it is recommended
to use while loop.
Syntax:
while(condition)
{
}

public class WhileExample
{
{
int i=1;
while(i<=10)
{
System.out.println(i);
i++;
}
} }
Output:
12345678910

• The Java do-while loop is used to iterate a part of the program
several times.
• If the number of iteration is not fixed and you must have to
execute the loop at least once, it is recommended to use do-
while loop.
• The Java do-while loop is executed at least once because
Condition is checked after loop body.
Syntax:
Do
{
}
while(condition);

public class DoWhileExample
{
{
int i=1;
do
{
System.out.print(i);
i++;
}
while(i<=8);
}
}
Output:
12345678

Control structures in java

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Control structures in java