Control statements in java with examples

• Programs in java will be executed in sequential manner means line by line execution of statements.
• By using control statements we can control the flow of execution.
• We have three types of control statements in java.

1. Decision making Statements.
2. Iteration statements.
3. Branching statements. 

1.Decision making statements in java: 

• In some cases we will have a situation like need to execution set of statements based on a condition
• In this scenario we need to use decision making statements in java.

1. if
2. if-else
3. if-else-if
4. switch

Simple if

• Based on some condition if we want to execute some set of statements then we need to use if condition in java.
• We need to keep all the required statements inside if block .
• If the condition is true then control executes the whole block otherwise it skips the if block of statements.

1. if( condition ){
2. // code
3. }
   

Java example program on if control statement:

1. package controlstatementsinjava;
2. import java.util.Scanner;
3.  
4. public class ControlStatementsInjava {
5.  
6.     /**
7.      * @website: www.instanceofjava.com
8.      */
9. public static void main(String[] args) {
10.         
11.   Scanner in= new Scanner(System.in);
12.  
13.   System.out.println("Please enter a number");
14.   int n=in.nextInt();
15.         
16. if(n%2==0){
17.    System.out.println(n+" is even number");
18.         
19.  }
20.   
21. if(n%2!=0){
22.      System.out.println(n+" is odd number");
23. }
25.  
26. }
27. }

Output:

1. Please enter a number
2. 5
3. 5 is odd number

If else condition:

• If the condition is true then control executes the whole block otherwise it skips the if block of statements
• if condition is false  if we need to execute another set of statement we can write another if and keep all the statements in that block.
• instead of checking multiple times we can simply use else block .
• More about in else statement in java

1. if( condition ){
2. // code
3. }else{
4. //code
5. }

 if else control statement with example programs:

1. package controlstatementsinjava;
2. import java.util.Scanner;
3.  
4. public class ControlStatementsInjava {
5.  
6.     /**
7.      * @website: www.instanceofjava.com
8.      */
9. public static void main(String[] args) {
10.         
11.   Scanner in= new Scanner(System.in);
12.  
13.   System.out.println("Please enter a number");
14.   int n=in.nextInt();
15.         
16. if(n%2==0){
17.    System.out.println(n+" is even number");
18.         
19.  }else{
20.      System.out.println(n+" is odd number");
21. }
22. 
    
23.  
24. }
25. }

Output:

1. Please enter a number
2. 5
3. 5 is odd number

if else ladder :

• In some cases we may get requirement with multiple conditions in such cases we need to use if else ladder.(if -else-if-else if -else...)

1. if( condition ){
2. // code
3. }else if{
4. //code
5. }else {
6.  //code
7. }

 if else if control statement with example programs:

1. package controlstatementsinjava;
2. import java.util.Scanner;
3.  
4. public class ControlStatementsInjava {
5.  
6.     /**
7.      * @website: www.instanceofjava.com
8.      */
9. public static void main(String[] args) {
10.         
11.   Scanner in= new Scanner(System.in);
12.  
13.   System.out.println("Please enter your age");
14.   int age=in.nextInt();
15.         
16. if(age<=18){
17.    System.out.println("Your age is between 1-18");
18.         
19.  }else if ((age>=18) && (age<=35)){
20.      System.out.println(" Your age is between 18-35");
21. }
22. else if ((age>=35) && (age<=50)){
23.      System.out.println(" Your age is between 35-50");
24. }else{
25.  
26.   System.out.println(" Your age is above 50");
27.  
28. }
29.  
30. }
31. }

Output:

1. Please enter your age
2. 20
3. Your age is between 18-35

Switch statement in java:

• Instead if writing number of if conditions we can use single switch statement

1. switch(value)
2.  case n1: statements;
3. break;
4. case n2 : statements;
5. break;
6. default: statements;
7. }

Java example program on switch statement in java: