control statements in java

Presented By Niloy Saha

Control Statements in Java

Department of Computer Science & Engineering

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Control Statements

Selection

Iteration

Jump

Outlines

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Selection

Selection Statements

Switch Statement

Selection Statements are also called Decision Making Statements.

Selection Statements

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if Statements

Simple if

if else

if- else- if Ladder

Nested if

if Statements

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Simple if Syntax :

if (condition){ statement1;}

Purpose: The statements will be evaluated if the value of the condition is true.

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Simple ifStart

End

Condition

Statements

FalseTrue

Flow Chart:

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Example

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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.

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if else

FalseTrue

Flow Chart: Start

End

Condition

Statement 1 Statement 2

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Example

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If-else-if LadderSyntax :

if(condition) statements;else if(condition) statements;else if(condition) statements;......else statements;

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Examplesimport 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"); } }}

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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....}

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Example

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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.

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switchFlow Chart:

Case A

Case B

…

default

False

False

False

Case A Statementsbreak;

Case B Statementsbreak;

Case C Statementsbreak;

Default Statements

Start

Variable or Expression

True

True

True

End

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Example

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Iteration StatementsIterations/ Loops

while

do while

for

Each loop has four types of statements :

Initialization Condition checking Execution Increment / Decrement

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whileSyntax:

initializationwhile(final value){ statements; increment/decrement;}

Purpose: To evaluate the statements from initial value to final value with given increment/decrement.

m=1while(m<=20){ System.out.println(m); m=m+1;}

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Exampleclass while1{ public static void main(String args[]) { int i=1; while(i<=10) { System.out.println("\n" + i); i++; } }}

Output :12345678910

print values from 1 to 10

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do whileSyntax:

initializationdo{ statements; increment/decrement;} while(final value);


m=1do{ System.out.println(m); m=m+1;}while(m==20);

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Exampleclass dowhile1{ public static void main(String args[]) { int i = 1; int sum = 0; do { sum = sum + i; i++; }while (i<=10); System.out.println("\n\n\tThe sum of 1 to 10 is .. " + sum); }}

Output :The sum of 1 to 10 is .. 55

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forSyntax:

for(initialization;final value;increment/decrement){ statements;}


for(m=1;m<=20;m=m+1){ System.out.println(m);}

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Exampleclass for1{ public static void main(String args[]) { 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

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Jump StatementsJump

break

continue

return

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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;

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Exampleclass break1{ public static void main(String args[]) { int i = 1; while (i<=10) { System.out.println("\n" + i); i++; if (i==5) { break; } } }}

Output :1234

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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.

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Exampleclass continue1{ public static void main(String args[]) { for (int i=1; i<1=0; i++) { if (i%2 == 0) continue; System.out.println("\n" + i); } }}

Output :13579

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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.

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Exampleclass Return1 { 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."); }}

Output :Before the return.

Thank You