Control statements in java

Topics for Today’s Session
What is JAVA
Control Statements in Java
Selection Statements
Looping Statements
Jumping Statements

Control Statements
 The Java control statements inside a program are usually
executed sequentially.
 Sometimes a programmer wants to break the normal flow and
jump to another statement or execute a set of statements
repeatedly.
 Control statements in java enables decision making, looping and
branching.
 A control statement in java is a statement that determines
whether the other statements will be executed or not.
 It controls the flow of a program.
 Control Statements can be divided into three categories,
namely
 Selection statements
 Iteration statements
 Jump statements

Decision-Making Statements
 Conditional Control Statements allows the program to
select between the alternatives during the program
execution.
 They are also called as decision-making statements or
selection statements.
 Statements that determine which statement to execute
and when are known as decision-making statements.
 These statements decides the flow of the execution based
on some conditions.
 Java’s Selection statements:
 if
 if-else
 nested-if
 if-else-if
 switch-case

Simple if statement
 if statement is the most simple decision making statement
 The if statement determines whether a code should be executed based on
the specified condition.
 if statement’s condition should evaluate only to the boolean values ‘true’
or ‘false’.
 We can add more than one condition in the same if statement by using
&& or || operators.
if(condition)
{
// statements (if Block)
}
//other statements

class IfDemo1 {
public static void main(String[] args)
{
int marks=70;
if(marks > 65)
{
System.out.print("Hello Java! Am in If");
}
}
}
if-then -else Statement
 The if-else statement is used for testing conditions.
 It is used for true as well as for false condition.
 If then Else statement provides two paths.
 The if block is executed when the condition holds true.
When the condition evaluates to false, the statements inside
the else block are executed.

if (condition)
{
// Executes this block if
// condition is true
}
else
{
// Executes this block if
// condition is false
}
contd..
// Java program to illustrate if-else statement
class IfElseDemo {
public static void main(String args[])
{
int i = 20;
if (i < 45)
System.out.println("i is smaller than 45");
else
System.out.println("i is greater than 55");
}
}

Nested if statement
An if present inside an if block is known as a nested if block.
It is similar to an if..else statement, except they are defined inside another
if..else statement.
contd..
if (condition1)
{
// Executes when condition1 is true
if (condition2)
{
// Executes when condition2 is true
}
}
class NestedIfDemo {
public static void main(String args[]) {
int s = 15;
if (s > 30)
{ if (s%2==0)
System.out.println("s is an even number and greater than 30!");
else
System.out.println("s is a odd number and greater than 30!"); }
else {
System.out.println("s is less than 15"); }
System.out.println("Hello World!");
} }

If Else-If ladder:
 If the condition is true, then it will execute the If block.
 Otherwise, it will execute the Else-If block.
 Again, if the condition is not met, then it will move to the else block.
 if-else-if ladder is used to decide among multiple options.
 The if statements are executed from the top down.
 As soon as one of the conditions controlling the if is true, the statement
associated with that if is executed, and the rest of the ladder is bypassed.
 If none of the conditions is true, then the final else statement will be
executed.

if(condition1)
{
//code for if condition1 is true
}
else if(condition2)
{
}
else if(condition3)
{
}
...
else
{
//code for all the false conditions
}

Switch statement
 The switch statement is a multiway branch statement.
 A switch statement is used to execute a single statement from multiple conditions.
 The switch statement can be used with short, byte, int, long, enum types, etc.
 One or N number of case values can be specified for a switch expression.
 Dulplicate case values are not allowed. A compile-time error is generated by the
compiler if unique values are not used.
 The case value must be literal or constant. Variables are not permissible.
 Usage of break statement is made to terminate the statement sequence. It is optional..
If this statement is not specified, the next case is executed.
 Based on the argument in the switch statement suitable case value will be selected and
executed.
 If no matching case found, then the default will be executed.
Switch(variable/value/expression){
Case :
// statements [];
Case :
// statements [];
…
default:
// statements [];
}

Looping Statements / Iter
ative Statements
 These are used to execute a block of statements multiple
times.
 It means it executes the same code multiple times until a
specified condition is met,
 These are also called Iteration statements.
 There are three types of looping control statements:
1. For loop
2. While loop
3. Do-while loop

While loop
 While loop is a control flow statement that allows code to be
executed repeatedly based on a given Boolean condition.
 The while loop can be thought of as a repeating if statement.
 It is used for iterating a part of the program several times.
 When the number of iteration is not fixed then while loop is
used.
 While loop executes till the condition becomes false.
while (test_expression)
{
// statements
update_expression;
}

class WhileDemo {
public static void main(String[] args) {
int i=1;
while(i<=10)
{
System.out.println(i);
i++;
}
} }
// Example for infinite while loop

do-while loop
 In Java, the do-while loop is used to execute a part of the program
again and again.
 do-while loop is an Exit control loop.
 If the number of iteration is not fixed then the do-while loop is
used.
 This loop executes at least once because the loop is executed before
the condition is checked.
 Therefore, unlike for or while loop, a do-while check for the
condition after executing the statements or the loop body.
do
{
//code for execution
}
while(condition);

// Program to display numbers 1 to 15 using do-while loop
class DoWhileDemo {
int i=1;
do {
System.out.println(i);
i++;
}while(i<=10);
} }
// Program for infinite do-while loop
class DoWhileDemoIn {
public static void main(String[] args)
{
do {
System.out.println("infinitive do while loop");
}while(true);
}
}

For loop:
 The for loop in java is used to iterate and evaluate a code multiple
times.
 When the number of iterations is known by the user, it is
recommended to use the for loop.
 In java there are 3 types of for loops, they are as follows:
1. Simple for loop
2. For-each loop
3. labelled for loop
for (initialization; condition; increment/decrement)
{
statement;
}

// Java program to illustrate for loop
class forLoopDemo {
// Writing a for loop
// to print Hello World 5 times
for (int i = 1; i <= 5; i++)
System.out.println("Hello World");
} }
// Program to display multiplication table
class ForDemo1 {
int n, i;
n=2;
for(i=1;i<=10;i++)
{
System.out.println(n+"*"+i+"="+n*i);
}
} }
Output:
2*1=2
2*2=4
2*3=6
2*4=8
2*5=10
2*6=12
2*7=14
2*8=16
2*9=18
2*10=20
Output:
Hello World
Hello World
Hello World
Hello World
Hello World

For-Each loop:
 The traversal of elements in an array can be done by the for-
each loop.
 The elements present in the array are returned one by one.
 It must be noted that the user does not have to increment the
value in the for-each loop.
for(Type var:array)
{
}
public class ForEachDemo1
{
inta[]={100,101,102,103,104};
for(int i:a)
{ System.out.println(i);
}
} }
Output:
100
101
102
103
104

Labelled For Loop
 In Java, Labelled For Loop is used to give label before any
for loop. It is very useful for nesting for loop.
labelname:
for(initialization;condition;incr/decr)
{
}
public class LabeledForDemo {
num:
for(inti=1;i<=5;i++)
{
num1:
for(int j=1;j<=5;j++)
{ if(i==2&&j==2)
{
break num;
}
System.out.println(i+"
"+j);
} }
}
}
Output:
1 1
1 2
1 3
1 4
1 5
2 1

 Branching statements are used to jump from the current
executing loop.
 Branching statements in java are used to jump from a statement
to another statement, thereby the transferring the flow of
execution
break Statement
 break is a keyword.
 It is used within any control statements.
 break – Terminates the loop or switch statement and transfers
execution to the statement immediately following the loop or
switch.
 The break statement in java is used to terminate a loop and
break the current flow of the program.
 Syntax:
break; or
break <label>;
Unconditional Control Statements /
Jump Statements / Branching statements

// Using break statement in for loop
Output:
0
1
2
3
4
5
After loop

continue Statement
 continue is a keyword.
 In Java, the Continue statement is used in loops.
 Continue statement is used to jump to the next iteration of the loop
immediately.
 It is used with for loop, while loop and do-while loop.
Syntax:
continue; or
continue<label>;
class continueTest {
for (int j = 0; j < 10; j++)
{
// If the number is odd then bypass and continue with next value
if (j%2 != 0)
continue;
// only even numbers will be printed
System.out.print(j + " ");
}
} }
Output: 0 2 4 6 8

//continue with label is used to continue the number of loops below
the label
class contlabelDemo{
public static void main(String args[]){
Termi:
for(int i=1;i<=4;i++)
{
for(int k=1;i<=4;k++)
{
System.out.print(“ ”+i+” ”);
if(i==3)
continue Termi;
System.out.println(“Hello”);
}
}
} }

Summary
 In this lesson you learnt about
 Control Statements
 Decision making statements
 Iterative statements
 Branching statements

Control statements in java

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Control statements in java