Summary  
This chapter demonstrates iterating through an array using a for loop, matching the loop counter to the array’s zero-based indexes and using array.length to prevent out-of-bounds access. It also shows printing each element sequentially in the loop without moving to a new line.

General domain of usage  
Text processing

## How to Iterate Through an Array Using Loops?

**Arrays** and **loops** are frequently used in tandem. When dealing with a large array containing **100** or even **1000** elements, manually working with and extracting each element would be impractical. Just imagine how time-consuming it would be to manually fill such an array...


To achieve such tasks, we'll employ **loops**. In the previous section, we observed that we initially assigned the variable ``i`` a value of ``0`` in the ``for`` loop, and array indexing also starts at ``0``.

Let's say we have a task to display all the elements of an array of type ``char`` with a length of ``10``. Let's examine a code fragment that accomplishes this task:


cGFja2FnZSBjb20uZXhhbXBsZTsKCnB1YmxpYyBjbGFzcyBNYWluIHsKICAgIHB1YmxpYyBzdGF0aWMgdm9pZCBtYWluKFN0cmluZ1tdIGFyZ3MpIHsKICAgICAgICAvLyBJbml0aWFsaXppbmcgYSBjaGFyIGFycmF5CiAgICAgICAgY2hhcltdIGNoYXJBcnJheSA9IHsnYycsICdvJywgJ2QnLCAnZScsICdmJywgJ2knLCAnbicsICdpJywgJ3QnLCAneSd9OwogICAgICAgIAogICAgICAgIC8vIFByaW50aW5nIHRoZSBhcnJheSB1c2luZyBhIGZvci1sb29wCiAgICAgICAgZm9yIChpbnQgaSA9IDA7IGkgPCBjaGFyQXJyYXkubGVuZ3RoOyBpKyspIHsKICAgICAgICAgICAgU3lzdGVtLm91dC5wcmludChjaGFyQXJyYXlbaV0pOwogICAgICAgIH0KICAgIH0KfQ==

Let's take a closer look at how the loop iterates over an array:

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

package com.example;

import org.junit.jupiter.api.DynamicTest;
import org.junit.jupiter.api.TestFactory;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;

import static org.junit.jupiter.api.Assertions.*;
import static org.junit.jupiter.api.DynamicTest.dynamicTest;

public class MainTest {

    @TestFactory
    Stream<DynamicTest> testCalculateAverage() {
        List<TestCase> testCases = List.of(
                new TestCase(new int[]{8, 8, 8, 8, 8, 8, 8, 8}, 8.0),
                new TestCase(new int[]{7, 8, 6, 9, 7, 7, 8, 7, 6, 9}, 7.4),
                new TestCase(new int[]{5, 5, 5, 5, 5, 5, 5, 5, 5, 5}, 5.0),
                new TestCase(new int[]{10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10}, 10.0),
                new TestCase(new int[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 0.0)
        );

        return testCases.stream().map(testCase -> {
            String inputStr = testCase.input == null ? "null" : toString(testCase.input);

            try {
                double actual = Main.calculateAverage(testCase.input);
                String name = Math.abs(actual - testCase.expected) < 0.0001
                        ? "Input: " + inputStr + " -> " + actual + " as expected."
                        : "Input: " + inputStr + " -> " + actual + ", expected: " + testCase.expected;

                return dynamicTest(name, () ->
                        assertEquals(testCase.expected, actual, 0.0001,
                                "Expected: " + testCase.expected + ", but got: " + actual));
            } catch (Exception e) {
                String name = "Runtime error: " + e.getClass().getSimpleName() + " - " + e.getMessage()
                        + " | Input: " + inputStr;

                return dynamicTest(name, () -> fail("Unexpected exception: " + e));
            }
        });
    }

    record TestCase(int[] input, double expected) {}

    private static String toString(int[] array) {
        return Arrays.toString(array);
    }
}


MainTest.java

A streamlined beginner module focused on the essential Java programming concepts: syntax, variables, data types, control flow, loops, arrays, and strings.

Using Loops with Arrays

How to Iterate Through an Array Using Loops?

解答