{"id":37,"date":"2019-01-15T02:22:35","date_gmt":"2019-01-15T02:22:35","guid":{"rendered":"https:\/\/kindsonthegenius.com\/java\/?p=37"},"modified":"2019-03-02T04:35:15","modified_gmt":"2019-03-02T04:35:15","slug":"06-java-constructors","status":"publish","type":"post","link":"https:\/\/kindsonthegenius.com\/java\/06-java-constructors\/","title":{"rendered":"Java – Constructors"},"content":{"rendered":"\n
  1. Introduction<\/a><\/li>
  2. Constructor with no Arguments<\/a><\/li>
  3. Parameterized Constructors<\/a><\/li>
  4. Creating new Objects<\/a><\/li><\/ol>\n\n\n\n

    <\/p>\n\n\n\n

    1. Introduction<\/h4>\n\n\n\n

    Constructors in Java are what we use to create new objects. Furthermore, you use a constructor on initialize new objects. Constructors have the same name as the class and not return type.<\/p>\n\n\n\n

    Generally, you assign initial values to instance variables using a constructor. But you can also perform some initial tasks required when a new object is created.<\/p>\n\n\n\n

    The code below give an example of a constructor.<\/p>\n\n\n

    <\/p>\n

    public<\/span> class<\/span> Vehicle<\/span> {<\/span>\n\tpublic<\/span> String make;<\/span>\n\t\n\tpublic<\/span> Vehicle<\/span>(<\/span>String make)<\/span> {<\/span> \/\/constructor with one parameter<\/span>\n\t\tthis<\/span>.<\/span>make<\/span> =<\/span> make;<\/span>\n\t}<\/span>\n}<\/span>\n<\/pre>\n<\/div>\n\n\n
    We have two types of constructors in Java.<\/p>\n\n\n\n
    • Constructor with no arguments<\/li>
    • Parameterized constructor<\/li><\/ul>\n\n\n\n
      <\/p>\n\n\n\n
      2. Constructors with no arguments<\/strong><\/h4>\n\n\n\n
      These constructors require not arguments. In this way you can create an object even if you don’t have the attributes. Take for example, the code below.<\/p>\n\n\n
      <\/p>\n
      public<\/span> class<\/span> Circle<\/span> {<\/span>\n\tint<\/span> radius;<\/span>\n\t\n\tpublic<\/span> Circle<\/span> ()<\/span> {<\/span> \/\/Constructor with no parameter<\/span>\n\t\tradius =<\/span> 50<\/span>;<\/span>\n\t}<\/span>\n}<\/span>\n<\/pre>\n<\/div>\n\n\n
      The constructor for circle has no parameters. However, when a new circle is created, it automatically has a radius of 50. Therefore if you run the code below, you will have an output of 50.<\/p>\n\n\n
      <\/p>\n
      public<\/span> class<\/span> Tester<\/span> {<\/span>\n\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String[]<\/span> args)<\/span> {<\/span>\n\t\tCircle circle =<\/span> new<\/span> Circle();<\/span>\n\t\t\n\t\tSystem.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>circle.<\/span>radius<\/span>);<\/span>\n\t}<\/span>\n}<\/span>\n<\/pre>\n<\/div>\n\n\n
      <\/p>\n\n\n\n
      3. Parameterized Constructors<\/strong><\/h4>\n\n\n\n
      Sometimes, you will need a constructor that accepts one or more parameters. You specify the parameter inside braces after the constructor name. An example is given below<\/p>\n\n\n
      <\/p>\n
      public<\/span> class<\/span> Circle<\/span> {<\/span>\n\tpublic<\/span> int<\/span> radius;<\/span>\n\t\n\tpublic<\/span> Circle<\/span> (<\/span>int<\/span> radius)<\/span> {<\/span> \/\/Parameterized constructor<\/span>\n\t\tthis<\/span>.<\/span>radius<\/span> =<\/span> radius;<\/span>\n\t}<\/span>\n}<\/span>\n<\/pre>\n<\/div>\n\n\n
      In the same way, you can run create a circle using the code below. <\/p>\n\n\n
      <\/p>\n
      public<\/span> class<\/span> Tester<\/span> {<\/span>\n\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String[]<\/span> args)<\/span> {<\/span>\n\t\tCircle circle =<\/span> new<\/span> Circle(<\/span>50<\/span>);<\/span>\n\t\t\n\t\tSystem.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>circle.<\/span>radius<\/span>);<\/span>\n\t}<\/span>\n}<\/span>\n<\/pre>\n<\/div>\n\n\n
      Running the above code would also produce similar result to the previous one. 50 is printed out. But notice that in this constructor, you pass 50 as a parameter.<\/p>\n\n\n\n
      Finally bear in mind, that two or even more constructors can be in the same class.<\/p>\n\n\n\n
      <\/p>\n\n\n\n
      4. Creating New Objects<\/strong><\/h4>\n\n\n\n
      Just as you know, objects are create from classes. You use the new keyword to create new objects from classes. <\/p>\n\n\n\n
      Note the three steps involved in creating new objects<\/p>\n\n\n\n
      • Declaration<\/strong>: Here, you specify a variable name as an object type<\/li>
      • Instantiation<\/strong>: You use the new keyword<\/li>
      • Initialization<\/strong>: Assign initial values<\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"
        Introduction Constructor with no Arguments Parameterized Constructors Creating new Objects 1. Introduction Constructors in Java are what we use to create new objects. Furthermore, you … <\/p>\n","protected":false},"author":395,"featured_media":38,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[2],"tags":[],"class_list":["post-37","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-tutorial"],"_links":{"self":[{"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/posts\/37","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/users\/395"}],"replies":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/comments?post=37"}],"version-history":[{"count":1,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/posts\/37\/revisions"}],"predecessor-version":[{"id":39,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/posts\/37\/revisions\/39"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/media\/38"}],"wp:attachment":[{"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/media?parent=37"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/categories?post=37"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/java\/wp-json\/wp\/v2\/tags?post=37"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}