Java Iteration Tutorial: How to Loop Through an Array in Java
Published: 2022-08-15 14:50:44

An `Array`is a collection of variables having values of the same type. Because `Arrays`are objects, they are reference types. An `Array`is essentially a memory reference to an `Array`object. To refer to a specific element in an `Array`, we supply the name of the `Array `reference and the element's position number in the `array`. The element's index is the element's position number.

## What Are Loops In Java
Java has looping statements, which allow programs to repeat statements as long as a condition is true. The first step in creating a Java loop is defining the statement that will be looped. In the second phase, the statement is wrapped in a loop. We'll go through the most frequent ones in this article so you can learn and understand how they function.

```
double[] grades = {96.5, 98.5, 99.3, 67, 90.1, 4, 67 };
```

## The While Loop
A while loop operates in such a way that it repeats statements repeatedly while the condition is true. The loop and program are ended if the condition is false.
Let's build a loop and provide the statement that will be looped.

```
int i = 0;
while (i <= 10){
    System.out.println(grades[i]);
    i++;
}
```
This will print out the element in each index

```
96.5
98.5
99.3
67.0
90.1
4.0
67.0
34.0
54.0
12.9
```
We output the students' grade values from 1 to 10 in the loop above. We start with `i=0` and increment it with `i++`. Because the last index is 10, the loop condition will terminate execution when `i = 10`. If we set `i=10` to true, the loop will loop indefinitely.

## The Do-While-Loop
The major difference between a `while `loop and a `do-while` loop is that the latter executes the loop body to determine whether the loop should be stopped or maintained.
Let's take a closer look at how `do-while` loops work.

```
do {
    System.out.println(grades[i]);
    i++;
} while (i <= 10);
```
this will print

```
96.5
98.5
99.3
67.0
90.1
4.0
67.0
34.0
54.0
12.9
```
In a `do-while loop`, if the condition is true, the loop body is executed `i = 10` and control updates the expression by either incrementing or decrementing i. If the condition is false, the loop breaks automatically.

## The For Loop
A `for-loop` provides a simplified syntax for creating loops. A loop is frequently written in the following format:

```
for (int j = 0; j <= 10; j++) {
    System.out.println(grades[j]);
}
```
This will print out the following

```
96.5
98.5
99.3
67.0
90.1
4.0
67.0
34.0
54.0
12.9
```
The for loop sets condition to 0, then repeats the println command and checks condition++ if condition is less than 10. The loop continuation condition is represented by Condition 10. The condition is verified both at startup and at the beginning of each iteration. If this condition is met, the loop body is performed. If it is false, the loop is terminated and the program control is transferred to the line after the loop.

## For Each Loop in Java.

To loop through `array `elements, the `for-each` loop is utilized. It is sometimes referred to as the `enhanced-loop.`
Let's have a look at how it works.

```
for (double grade: grades) {
    System.out.println(grade);
}
```
the out put of this would be the following

```
96.5
98.5
99.3
67.0
90.1
4.0
67.0
34.0
54.0
12.9
```
What differentiates `for-each` loop from every other is, here, we print each elements of grades one by one. It is not quite different from other loops we have discussed.

## Finishing up
Finally, because of the continuation condition, `while` and `for-loops `are referred to as "**pretest loops**," which means they are checked before the loop body is executed. The `do-while` loop is known as a "**posttest loop**." This also indicates that the condition is checked once the loop body is finished. The three loop various types are interchangeable.

A loop of any of these loop types, such as a `while-loop`, may always be modified into a `for-loop` or `enhance-loop`. `While`, `do-while`, and `for-loop` all express the same thing and can be used interchangeably.