{"id":5290,"date":"2021-03-23T17:02:51","date_gmt":"2021-03-23T17:02:51","guid":{"rendered":"https:\/\/ded9.com\/?p=5290"},"modified":"2025-10-25T09:46:00","modified_gmt":"2025-10-25T09:46:00","slug":"the-basics-of-arrays-in-java","status":"publish","type":"post","link":"https:\/\/ded9.com\/de\/the-basics-of-arrays-in-java\/","title":{"rendered":"Understanding Arrays in Java: A Beginner’s Guide"},"content":{"rendered":"

In this tutorial, you will learn how to work with\u00a0<\/span>arrays in Java:<\/span> Define, initialize, and access elements with examples.<\/span><\/span><\/p>\n

An array is a container that holds data (values) of a single type. For example, you can create an array having 100 int values.<\/p>\n

An array is a basic structure in Java that allows you to store and access large amounts of values easily.<\/p>\n

How to define an array<\/a>?<\/span><\/h1>\n

Here is how to define an array in Java<\/a>:<\/p>\n

\n
dataType [] arrayName;<\/pre>\n<\/div>\n
    \n
  • dataType can be a raw data type, such as int, char, Double, byte, etc., or an object<\/li>\n
  • arrayName is the identifier.<\/li>\n<\/ul>\n
    Let us repeat the above example.<\/p>\n
    \n
    double [] data;<\/pre>\n<\/div>\n
    Here, data is an array that can hold values \u200b\u200bof type Double.<\/p>\n
    But how many elements can the data array hold?<\/span><\/h2>\n
    That was a good question!\u00a0We have not defined it yet.\u00a0The next step is to allocate memory for the array elements.<\/p>\n
    \n
    data = new Double [10];<\/p>\n<\/blockquote>\n
    The data array’s length is 10. This means it can hold 10 elements (in this case, 10 double values).<\/p>\n
    Note that once the array length is defined, it cannot be changed during the program.<\/p>\n
    Let’s take another example:<\/p>\n
    \n
    int [] age;\r\n\r\nage = new int [5];<\/pre>\n<\/div>\n
    Here, the age array can hold five values \u200b\u200bof type int.<\/p>\n
    In one command, the memory of an array can be declared and allocated. You can replace the above two sentences with a single sentence.<\/p>\n
    \n
    int [] age = new int [5];<\/pre>\n<\/div>\n
    Array Index in Java<\/span><\/h1>\n
    You can access elements of an array using indexes.\u00a0Consider the previous example.<\/p>\n
    \n
    int [] age = new int [5];<\/p>\n<\/blockquote>\n
    \"Array<\/p>\n
    The first element of the array is [age [0]], the second element is [age [1], and …<\/p>\n
    If the array length is n, the last element will be [arrayName] n-1.\u00a0Since the length of the age array is 5, the last element of the array in the example above is age.<\/p>\n
    The default initial value of the elements of an array is 0 for all numeric types and false for booleans. Consider the following example:<\/p>\n
    \n
      \n
    1. class ArrayExample {<\/li>\n
    2. public static void main (String [] args) {<\/li>\n
    3. <\/li>\n
    4. int [] age = new int [5];<\/li>\n
    5. <\/li>\n
    6. System.out.println (age [0]);<\/li>\n
    7. System.out.println (age [1]);<\/li>\n
    8. System.out.println (age [2]);<\/li>\n
    9. System.out.println (age [3]);<\/li>\n
    10. System.out.println (age [4]);<\/li>\n
    11. }<\/li>\n
    12. }<\/li>\n<\/ol>\n<\/blockquote>\n
      Output<\/h3>\n
      \n
      \u06f0<\/p>\n
      \u06f0<\/p>\n
      \u06f0<\/p>\n
      \u06f0<\/p>\n
      \u06f0<\/p>\n<\/blockquote>\n
      There is a better way to access the elements of an array using a loop structure (usually, a for loop is used).<\/h4>\n
      \n
        \n
      1. class ArrayExample {<\/li>\n
      2. public static void main (String [] args) {<\/li>\n
      3. int [] age = new int [5];<\/li>\n
      4. for (int i = 0; i <5; ++ i) {<\/li>\n
      5. System.out.println (age [i]);<\/li>\n
      6. }<\/li>\n
      7. }<\/li>\n
      8. }<\/li>\n<\/ol>\n<\/blockquote>\n
        How do I initialize arrays in Java?<\/span><\/h1>\n
        In Java, you can set arrays when defining or later define or modify values according to your needs.<\/p>\n
        Initialize the array when defining<\/strong><\/span><\/h2>\n
        Here’s how to set an array when defining.<\/p>\n
        \n
        int [] age = {12, 4, 5, 2, 5};<\/pre>\n<\/div>\n
        This expression creates an array and values \u200b\u200bit when defining it.<\/p>\n
        The array’s length is determined by the number of values \u200b\u200bseparated by commas. In this example, it is 5.<\/p>\n
        \"This<\/p>\n
        Let’s write a simple program to print the elements of this array.<\/h3>\n
        \n
          \n
        1. class ArrayExample {<\/li>\n
        2. public static void main (String [] args) {<\/li>\n
        3. int [] age = {12, 4, 5, 2, 5};<\/li>\n
        4. for (int i = 0; i <5; ++ i) {<\/li>\n
        5. System.out.println (\u201cElement at index\u201d + i + \u201d:\u201d + age [i]);<\/li>\n
        6. }<\/li>\n
        7. }<\/li>\n
        8. }<\/li>\n<\/ol>\n<\/blockquote>\n
          The output of the above code is equal to:<\/p>\n
          \n
          Element at index 0:12<\/p>\n
          Element at index 1: 4<\/p>\n
          Element at index 2: 5<\/p>\n
          Element at index 3: 2<\/p>\n
          Element at index 4: 5<\/p>\n<\/blockquote>\n
          How to access array elements?<\/span><\/h1>\n
          Using its numeric list, you can easily access and modify array elements.\u00a0Let’s give an example.<\/p>\n
          \n
            \n
          1. class ArrayExample {<\/li>\n
          2. public static void main (String [] args) {<\/li>\n
          3. int [] age = new int [5];<\/li>\n
          4. \/\/ insert 14 to third element<\/li>\n
          5. age [2] = 14;<\/li>\n
          6. \/\/ insert 34 to first element<\/li>\n
          7. age [0] = 34;<\/li>\n
          8. for (int i = 0; i <5; ++ i) {<\/li>\n
          9. System.out.println (\u201cElement at index\u201d + i + \u201d:\u201d + age [i]);<\/li>\n
          10. }<\/li>\n
          11. }<\/li>\n
          12. }<\/li>\n<\/ol>\n<\/blockquote>\n
            Output<\/strong><\/h4>\n
            \n
            Element at index 0:34<\/p>\n
            Element at index 1: 0<\/p>\n
            Element at index 2:14<\/p>\n
            Element at index 3: 0<\/p>\n
            Element at index 4: 0<\/p>\n<\/blockquote>\n
            Example: Arrays in Java<\/strong><\/h3>\n
            The following program calculates the sum and average of the values \u200b\u200bstored in an int array.<\/p>\n
            \n
              \n
            1. class SumAverage {<\/li>\n
            2. public static void main (String [] args) {<\/li>\n
            3. int [] numbers = {2, -9, 0, 5, 12, -25, 22, 9, 8, 12};<\/li>\n
            4. int sum = 0;<\/li>\n
            5. Double average;<\/li>\n
            6. <\/li>\n
            7. for (int number: numbers) {<\/li>\n
            8. sum + = number;<\/li>\n
            9. }<\/li>\n
            10. <\/li>\n
            11. int arrayLength = numbers.length;<\/li>\n
            12. \/\/ Change sum and arrayLength to double as average is in double<\/li>\n
            13. average = ((double) sum \/ (double) arrayLength);<\/li>\n
            14. System.out.println (\u201cSum =\u201d + sum);<\/li>\n
            15. System.out.println (\u201cAverage =\u201d + average);<\/li>\n
            16. }<\/li>\n
            17. }<\/li>\n<\/ol>\n<\/blockquote>\n
              Output<\/strong><\/h3>\n
              \n
              Sum = 36<\/p>\n
              Average = 3.6<\/p>\n<\/blockquote>\n
                \n
              • Each loop is used to access each array element.<\/li>\n
              • To calculate the mean, the sum of the integers and the array length are doubled because the mean is double. This is called data type conversion.<\/li>\n
              • The length property is used to get the array length. Here, numbers. Length returns the length of the array of numbers.<\/li>\n<\/ul>\n
                Multidimensional arrays<\/h2>\n
                The arrays we have mentioned so far are called one-dimensional arrays. In Java, you can define an array of multidimensional arrays. Here is an example of how to define and initialize a multidimensional array.<\/p>\n
                \n
                Double [] [] matrix = {{1.2, 4.3, 4.0},\r\n\r\n{4 \u066b 1, -1 \u066b 1}\r\n\r\n};<\/pre>\n<\/div>\n
                Here, the matrix is \u200b\u200ba 2D array.<\/p>\n
                FAQ<\/h2>\n
                \n
                \n
                \n
                What is an array in Java?<\/h3>\n
                \n\n
                An array in Java is a data structure that stores multiple values of the same type in a single variable, accessible via indices.<\/p>\n\n<\/div>\n<\/div>\n
                \n
                How do you declare an array in Java?<\/h3>\n
                \n\n
                Use the syntax dataType[] arrayName; or dataType arrayName[]; followed by initialization, e.g., arrayName = new dataType[size];.<\/p>\n\n<\/div>\n<\/div>\n
                \n
                Can arrays in Java hold different data types?<\/h3>\n
                \n\n
                No, arrays in Java are homogeneous; they can only store elements of the same data type.<\/p>\n\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
                In this tutorial, you will learn how to work with\u00a0arrays in Java: Define, initialize, and access elements with examples. An array is a container that holds data (values) of a single type. For example, you can create an array having 100 int values. An array is a basic structure in Java that allows you to […]<\/p>\n","protected":false},"author":6,"featured_media":5291,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[11513],"tags":[840],"class_list":["post-5290","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-2","tag-java"],"acf":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/posts\/5290","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/comments?post=5290"}],"version-history":[{"count":6,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/posts\/5290\/revisions"}],"predecessor-version":[{"id":263899,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/posts\/5290\/revisions\/263899"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/media\/5291"}],"wp:attachment":[{"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/media?parent=5290"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/categories?post=5290"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ded9.com\/de\/wp-json\/wp\/v2\/tags?post=5290"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}