Java Loop Statements, Java Control Flow, Java for loop, while loop, do while loop, enhanced for loop, and Java nested loop statements.
Looping in programming languages is a feature that facilitates the execution of a set of instructions/functions repeatedly while some condition evaluates to true.
Loop Statements in Java
We have four loop structures in Java,
1. for loop
2. while loop
3. do while loop
4. enhanced for loop
1. for loop
Description: It repeats a block of statements for a specified number of times
Syntax:
for (Initialization/Start Value; Condition/End Value; Increment or Decrement){
statements
.
.
}
Example 1: Print 1 to 10 Numbers
for (int i=1; i<=10; i++) {
System.out.println(i);
}
Example 2: Print even numbers up to 20
for (int i=2; i<=20; i+=2) {
System.out.println(i);
}
Example 3: Print 1 to 5 Numbers except 4th Number
for (int i=1; i<=5; i++) {
if (i!=4) {
System.out.println(i);
}
}
Example 4: Print 1 to 10 in reverse order except 4th and 7th Orders
for (int i=10; i>=1; i–) {
if ((i!=4)&&(i!=7)) {
System.out.println(i);
}
}
2. while loop
Description: It repeats a block of statements while the condition is true
Syntax:
Initialization;
while (condition){
statements
.
.
increment/decrement;
}
Example 1: Print 1 to 10 Numbers…
int i=1;
while (i<=10){
System.out.println(i);
i++;
}
Example 2: Print 1 to 5 Numbers except 4th Number
while (i<=5){
if (i!=4){
System.out.println(i);
}
i++;
}
Example 3: Print 1 to 10 Numbers in reverse Order
int i=10;
while (i>=1){
System.out.println(i);
i–;
}
Example 4: Print 1 to 10 Numbers in reverse Order except 4th and 9th numbers
int i=10;
while (i>=1){
if ((i!=4) && (i!=9)){
System.out.println(i);
}
i–-;
}
3. do while loop
Description: It repeats a block of statements while the condition is true and it executes statements at least once irrespective of the condition
Syntax:
Initialization;
do
{
Statements
.
.
Increment/Decrement;
} while (condition);
Example 1: Print 1 to 10 Numbers…
int i=1;
do
{
System.out.println(i);
i++;
} while(i<=10);
Example 2:
int i=20;
do
{
System.out.println(i);
i++;
} while(i<=10);
Example 3: Print 1 to 10 Numbers in reverse order
int i=10;
do
{
System.out.println(i);
i–;
} while(i>=1);
Example 4: Print 1 to 5 Numbers except 3rd Number
do
{
if (i!=3){
System.out.println(i);
}
i++;
} while(i<=5);
4. Enhanced for loop
It executes all elements in an Array
Syntax:
Array Declaration;
for (declaration: Expression/Array){
Statements
.
.
}
Example 1:
String [] languages={“COBOL”, “C”, “Java”, “VBScript”};
for (String lang: languages){
System.out.println(lang);
Example 2:
public static void main(String[] args) {
int a=10, b=5;
int [] mathOperations = new int[3];
mathOperations[0]= a+b;
mathOperations[1]= a-b;
for (int operation: mathOperations){
System.out.println(operation);
}
