The output result of Java array is abnormal after expansion. What is the problem?

Java array expansion and output result analysis

This article analyzes a piece of Java code. The code intends to achieve dynamic expansion of the array, but the output results do not match expectations. We will analyze the root causes of the problem and provide solutions.

The code is designed to add element 4 to the end of the array int[] arr = {1, 2, 3} , making it {1, 2, 3, 4} . The code creates a new array, copies the original array element, adds a new element, and assigns the new array to the original array variable.

The original code is as follows:

 public class AddToArray {
    public static void main(String[] args) {
        int arr1[] = {1, 2, 3};
        int arr2[] = new int[arr1.length 1];

        for (int i = 0; i <p> The program expects output 1 2 3 4, but the actual output may be different from expected, depending on the running environment and <code>System.out.println(arr1[i] '\t');</code> this line of code.</p><p> <strong>Problem analysis:</strong></p><p> <code>System.out.println(arr1[i] '\t');</code><code> </code>Operators are not simple string concatenation. Since <code>'\t'</code> is a tab, it has the ASCII code value of 9. Java will add the integer <code>arr1[i]</code> to the integer 9, and then convert the result to a string output. This results in the output not the array element itself.</p><p> <strong>Solution:</strong></p><p> To avoid integer addition, <code>'\t'</code> should be stringed with <code>arr1[i]</code> , or output <code>arr1[i]</code> directly. The modified code is as follows:</p><pre class="brush:php;toolbar:false"> public class AddToArray {
    public static void main(String[] args) {
        int arr1[] = {1, 2, 3};
        int arr2[] = new int[arr1.length 1];

        for (int i = 0; i <p> or:</p><pre class="brush:php;toolbar:false"> public class AddToArray {
    public static void main(String[] args) {
        int arr1[] = {1, 2, 3};
        int arr2[] = new int[arr1.length 1];

        for (int i = 0; i <p> The modified code will correctly output "1 2 3 4" (or "1234" if the second modification scheme is used). This emphasizes that subtle symbolic errors in programming can lead to unexpected results and requires careful examination of code details. In addition, it should be noted that Java arrays are reference types, <code>arr1 = arr2;</code> this line points the reference of <code>arr1</code> to the new array <code>arr2</code> , rather than copying the array content. </p><p><img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/001/246/273/174269882678747.jpg?x-oss-process=image/resize,p_40" class="lazy" alt="The output result of Java array is abnormal after expansion. What is the problem?"></p>

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