Control statements in java programmng

 Control statements are used in programming languages to cause the
flow of control to advance and branch based on changes to the state
of a program.
 In Java, control statements can be divided under the following three
categories:
 Selection statements
 Iteration statements
 Jump statements
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ControlStatements

 Selection statements are used in a program to choose different paths
of execution based upon the outcome of an expression or the state of
a variable.
 Using if and if...else
 Nested if Statements
 Using switch Statements
 Conditional Operator
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ControlStatements
Principal forms:

 Additional forms
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if( a > b)
{
System.out.println("A = " + a + "tB = " +
b);
System.out.println("A is greater than B");
}
else
{
System.out.println("A = " + a + "tB = " +
b);
System.out.println("Either both are equal
or B is greater");
}
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ControlStatements
class Example4_2
{
public static void main(String Args[])
{
int a = 3;
if (a <= 10 && a > 0)
{
System.out.println("Number is valid.");
if ( a < 5)
System.out.println("From 1 to 5");
else
System.out.println("From 5 to 10");
}
else
System.out.println("Number is not valid");
}
}

class Example4_1{
public static void main (String Args[]){
int a = 5;
boolean val = false;
if(val)
System.out.println("val is false, so it won't execute";
else if (a < 0 )
System.out.println("A is a negative value");
else if (a > 0)
System.out.println ("A is a positive value");
else
System.out.println ("A is equal to zero");
}
}
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class Example4_3{
public static void main(String Args[]){
int month = 3;
switch (month){
case 1:
System.out.println("The month of January");
break;
case 2:
System.out.println("The month of February");
break;
case 3:
System.out.println("The month of March");
break;
case 4:
System.out.println("The month of April");
break; case 5:
System.out.println("The month of May");
break;
case 6:
System.out.println("The month of June");
break;
case 7:
System.out.println("The month of July");
break;
case 8:
System.out.println("The month of August");
break;
case 9:
System.out.println("The month of September");
break;
case 10:
System.out.println("The month of October");
break;
case 11:
System.out.println("The month of November");
break;
case 12:
System.out.println("The month of December");
break;
default:
System.out.println("Invalid month");
}
}
}

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ControlStatements
// Returns the smallest n
// such that 2^n >= x
public static int intLog2 (int x)
{
int n = 0, p = 1;
while ( p < x )
{
p *= 2;
n++;
}
return n;
}
Initialization
Testing
Change

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ControlStatements
 for is a shorthand that combines in one statement initialization,
condition, and change
for ( initialization; condition; change )
{
statement1;
statement2;
...
statementN;
}

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ControlStatements
// Returns the smallest n
// such that 2^n >= x
public static int intLog2 (int x)
{
int n = 0, p;
for (p = 1; p < x; p *= 2)
{
n++;
}
return n;
}
Initialization
Testing
Change

public class DoWhileExample
{
public static void main (String[ ] args)
{
int i =0;
do
{
System.out.println ("i is : " + i);
i++;
} while (i < 4);
}
}
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ControlStatements

 Break in a loop instructs the program to immediately quit the current
iteration and go to the first statement following the loop.
SYNTAX break label;
 Break statement has two forms:
 Labeled Break statement
 Unlabeled Break statement
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ControlStatements

 Labeled Break
for(int var =0; var < 5 ; var++)
{
System.out.println(“Var is : “ + var);
if(var == 3)
break;
}
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ControlStatements
oUnlabeled Break
Outer:
for(int var1=0; var1 < 5 ; var1++)
{
for(int var2 = 1; var2 < 5;var2++)
{
System.out.println(“var1:” +
var1 + “, var2:” + var2);
if(var1 == 3)
break Outer;
}
}

 Continue statement is used when we want to skip the rest of the
statement in the body of the loop and continue with the next
iteration of the loop.
SYNTAX continue label;
 There are two forms of continue statement in Java.
 Unlabeled Continue Statement
 Labeled Continue Statement
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o Labeled Continue
Outer:
for(int var1 =0; var1 < 5 ; var1++)
{
for(int var2=0 ; var2 < 5 ; var2++)
{
if(var2 == 2)
continue Outer;
System.out.println(“var1:” + var1
+ “, var2:”+ var2);
}
}
oUnlabeled Continue
for(int var1 =0; var1 < 5 ; var1++)
{
for(int var2=0 ; var2 < 5 ; var2++)
{
if(var2 == 2)
continue;
System.out.println(“var1:” +
var1 + “, var2:”+ var2);
}
}

 Return in a loop instructs the program to immediately quit the
current method and return to the calling method.
 Example
class Return
{
public static void main(String args[])
{
boolean t = true;
System.out.println("Before the return.");
if(t) return; // return to caller
System.out.println("This won't execute.");
}
}
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ControlStatements

Control statements in java programmng

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