Complete Java Notes for Beginners & BCA/College Students

Java Control Statements | Control Flow in Java
Java compiler executes the code from top to bottom. The statements in the code are executed
according to the order in which they appear. However, Java provides statements that can be
used to control the flow of Java code. Such statements are called control flow statements. It is
one of the fundamental features of Java, which provides a smooth flow of program.

Java provides three types of control flow statements.

1.​ Decision Making statements
○​ if statements
○​ switch statement
2.​ Loop statements
○​ do while loop
○​ while loop
○​ for loop
○​ for-each loop
3.​ Jump statements
○​ break statement
○​ continue statement

Decision-Making statements:
As the name suggests, decision-making statements decide which statement to execute and
when. Decision-making statements evaluate the Boolean expression and control the program
flow depending upon the result of the condition provided. There are two types of
decision-making statements in Java, i.e., If statement and switch statement.

1) If Statement:
In Java, the "if" statement is used to evaluate a condition. The control of the program is diverted
depending upon the specific condition. The condition of the If statement gives a Boolean value,
either true or false. In Java, there are four types of if-statements given below.
1.​ Simple if statement
2.​ if-else statement
3.​ if-else-if ladder
4.​ Nested if-statement



1.​ Simple if statement:
It is the most basic statement among all control flow statements in Java. It evaluates a
Boolean expression and enables the program to enter a block of code if the expression
evaluates to true.
Syntax of if statement is given below.
​ if(condition) {
​ statement 1; //executes when condition is true
​ }

, Consider the following example in which we have used the if statement in the java code.
Student.java

public class Student {
public static void main(String[] args) {
int x = 10;
int y = 12;
if(x+y > 20) {
System.out.println("x + y is greater than 20");
}
}
}
Output:
x + y is greater than 20

2.​ if-else statement
The if-else statement is an extension to the if-statement, which uses another block of
code, i.e., else block. The else block is executed if the condition of the if-block is
evaluated as false.

Syntax:

if(condition) {
statement 1; //executes when condition is true
}
else{
statement 2; //executes when condition is false
}
Consider the following example.
Student.java

public class Student {
public static void main(String[] args) {
int x = 10;
int y = 12;
if(x+y < 10) {
System.out.println("x + y is less than 10");
} else {
System.out.println("x + y is greater than 20");
}
}
}
Output:
x + y is greater than 20

,3.​ if-else-if ladder:
The if-else-if statement contains the if-statement followed by multiple else-if statements.
In other words, we can say that it is the chain of if-else statements that create a decision
tree where the program may enter in the block of code where the condition is true. We
can also define an else statement at the end of the chain.

Syntax of if-else-if statement is given below.

if(condition 1) {
statement 1; //executes when condition 1 is true
}
else if(condition 2) {
statement 2; //executes when condition 2 is true
}
else {
statement 2; //executes when all the conditions are false
}

Student.java

public class Student {
public static void main(String[] args) {
String city = "Delhi";
if(city == "Meerut") {
System.out.println("city is meerut");
}else if (city == "Noida") {
System.out.println("city is noida");
}else if(city == "Agra") {
System.out.println("city is agra");
}else {
System.out.println(city);
}
}
}
Output:
Delhi

4.​ Nested if-statement
In nested if-statements, the if statement can contain a if or if-else statement inside
another if or else-if statement.

Syntax of Nested if-statement is given below.

if(condition 1) {

, statement 1; //executes when condition 1 is true
if(condition 2) {
statement 2; //executes when condition 2 is true
}
else{
statement 2; //executes when condition 2 is false
}
}

Consider the following example.
Student.java

public class Student {
public static void main(String[] args) {
String address = "Delhi, India";

if(address.endsWith("India")) {
if(address.contains("Meerut")) {
System.out.println("Your city is Meerut");
}else if(address.contains("Noida")) {
System.out.println("Your city is Noida");
}else {
System.out.println(address.split(",")[0]);
}
}else {
System.out.println("You are not living in India");
}
}
}
Output:
Delhi

Switch Statement:
In Java, Switch statements are similar to if-else-if statements. The switch statement contains
multiple blocks of code called cases and a single case is executed based on the variable which
is being switched. The switch statement is easier to use instead of if-else-if statements. It also
enhances the readability of the program.

Points to be noted about switch statement:

The case variables can be int, short, byte, char, or enumeration. String type is also supported
since version 7 of Java
Cases cannot be duplicate