In this tutorial, we will learn about the super keyword in Java with the help of examples.<\/p>\n\n\n\n
The super<\/code> keyword in Java is used in subclasses to access superclass members (attributes, constructors and methods).<\/p>\n\n\n\n
Before we learn about the\u00a0super<\/code>\u00a0keyword, make sure to know about\u00a0Java inheritance.<\/p>\n\n\n\n\n\n\n\n
Uses of super keyword<\/h2>\n\n\n\n
To call methods of the superclass that is overridden in the subclass.<\/li>
To access attributes (fields) of the superclass if both superclass and subclass have attributes with the same name.<\/li>
To explicitly call superclass no-arg (default) or parameterized constructor from the subclass constructor.<\/li><\/ol>\n\n\n\n
Let\u2019s understand each of these uses.<\/p>\n\n\n\n
\n\n\n\n
1. Access Overridden Methods of the superclass<\/h2>\n\n\n\n
If methods with the same name are defined in both superclass and subclass, the method in the subclass overrides the method in the superclass. This is called\u00a0method overriding.<\/p>\n\n\n\n
Example 1: Method overriding<\/h3>\n\n\n\n
class Animal {\n\n \/\/ overridden method\n public void display(){\n System.out.println(\"I am an animal\");\n }\n}\n\nclass Dog extends Animal {\n\n \/\/ overriding method\n @Override\n public void display(){\n System.out.println(\"I am a dog\");\n }\n\n public void printMessage(){\n display();\n }\n}\n\nclass Main {\n public static void main(String[] args) {\n Dog dog1 = new Dog();\n dog1.printMessage();\n }\n}\n<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
I am a dog\n<\/samp><\/code><\/pre>\n\n\n\n
In this example, by making an object dog1<\/var> of Dog<\/var> class, we can call its method printMessage()<\/var> which then executes the display()<\/code> statement.<\/p>\n\n\n\n
Since display()<\/code> is defined in both the classes, the method of subclass Dog<\/var> overrides the method of superclass Animal<\/var>. Hence, the display()<\/code> of the subclass is called.<\/p>\n\n\n\n<\/figure>\n\n\n\n
What if the overridden method of the superclass has to be called?<\/strong><\/p>\n\n\n\n
We use super.display()<\/code> if the overridden method display()<\/code> of superclass Animal<\/var> needs to be called.<\/p>\n\n\n\n
Example 2: super to Call Superclass Method<\/h3>\n\n\n\n
class Animal {\n\n \/\/ overridden method\n public void display(){\n System.out.println(\"I am an animal\");\n }\n}\n\nclass Dog extends Animal {\n\n \/\/ overriding method\n @Override\n public void display(){\n System.out.println(\"I am a dog\");\n }\n\n public void printMessage(){\n\n \/\/ this calls overriding method\n display();\n\n \/\/ this calls overridden method\n super.display();\n }\n}\n\nclass Main {\n public static void main(String[] args) {\n Dog dog1 = new Dog();\n dog1.printMessage();\n }\n}\n<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
I am a dog\nI am an animal\n<\/samp><\/code><\/pre>\n\n\n\n
Here, how the above program works.<\/p>\n\n\n\n<\/figure>\n\n\n\n\n\n\n\n
2. Access Attributes of the Superclass<\/h2>\n\n\n\n
The superclass and subclass can have attributes with the same name. We use the super<\/code> keyword to access the attribute of the superclass.<\/p>\n\n\n\n
Example 3: Access superclass attribute<\/h3>\n\n\n\n
class Animal {\n protected String type=\"animal\";\n}\n\nclass Dog extends Animal {\n public String type=\"mammal\";\n\n public void printType() {\n System.out.println(\"I am a \" + type);\n System.out.println(\"I am an \" + super.type);\n }\n}\n\nclass Main {\n public static void main(String[] args) {\n Dog dog1 = new Dog();\n dog1.printType();\n }\n}\n<\/code><\/pre>\n\n\n\n
Output<\/strong>:<\/p>\n\n\n\n
I am a mammal\nI am an animal\n<\/samp><\/code><\/pre>\n\n\n\n
In this example, we have defined the same instance field type<\/var> in both the superclass Animal<\/var> and the subclass Dog<\/var>.<\/p>\n\n\n\n
We then created an object dog1<\/var> of the Dog<\/var> class. Then, the printType()<\/code> method is called using this object.<\/p>\n\n\n\n
Inside the printType()<\/code> function,<\/p>\n\n\n\n
type<\/var> refers to the attribute of the subclass Dog<\/var>.<\/li>
super.type<\/var> refers to the attribute of the superclass Animal.<\/li><\/ul>\n\n\n\n
Hence, System.out.println(\"I am a \" + type);<\/code> prints I am a mammal<\/samp>. And, System.out.println(\"I am an \" + super.type);<\/code> prints I am an animal<\/samp>.<\/p>\n\n\n\n\n\n\n\n
3. Use of super() to access superclass constructor<\/h2>\n\n\n\n
As we know, when an object of a class is created, its default constructor is automatically called.<\/p>\n\n\n\n
To explicitly call the superclass constructor from the subclass constructor, we use super()<\/code>. It’s a special form of the super<\/code> keyword.<\/p>\n\n\n\n
super()<\/code> can be used only inside the subclass constructor and must be the first statement.<\/p>\n\n\n\n
Example 4: Use of super()<\/h3>\n\n\n\n
class Animal {\n\n \/\/ default or no-arg constructor of class Animal\n Animal() {\n System.out.println(\"I am an animal\");\n }\n}\n\nclass Dog extends Animal {\n\n \/\/ default or no-arg constructor of class Dog\n Dog() {\n\n \/\/ calling default constructor of the superclass\n super();\n\n System.out.println(\"I am a dog\");\n }\n}\n\nclass Main {\n public static void main(String[] args) {\n Dog dog1 = new Dog();\n }\n}\n<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
I am an animal\nI am a dog\n<\/samp><\/code><\/pre>\n\n\n\n
Here, when an object dog1<\/var> of Dog<\/var> class is created, it automatically calls the default or no-arg constructor of that class.<\/p>\n\n\n\n
Inside the subclass constructor, the super()<\/code> statement calls the constructor of the superclass and executes the statements inside it. Hence, we get the output I am an animal<\/samp>.<\/p>\n\n\n\n<\/figure>\n\n\n\n
The flow of the program then returns back to the subclass constructor and executes the remaining statements. Thus, I am a dog<\/samp> will be printed.<\/p>\n\n\n\n
However, using super()<\/code> is not compulsory. Even if super()<\/code> is not used in the subclass constructor, the compiler implicitly calls the default constructor of the superclass.<\/p>\n\n\n\n
So, why use redundant code if the compiler automatically invokes super()?<\/strong><\/p>\n\n\n\n
It is required if the parameterized constructor (a constructor that takes arguments)<\/strong> of the superclass has to be called from the subclass constructor.<\/p>\n\n\n\n
The parameterized super()<\/code> must always be the first statement in the body of the constructor of the subclass, otherwise, we get a compilation error.<\/p>\n\n\n\n
Example 5: Call Parameterized Constructor Using super()<\/h3>\n\n\n\n
class Animal {\n\n \/\/ default or no-arg constructor\n Animal() {\n System.out.println(\"I am an animal\");\n }\n\n \/\/ parameterized constructor\n Animal(String type) {\n System.out.println(\"Type: \"+type);\n }\n}\n\nclass Dog extends Animal {\n\n \/\/ default constructor\n Dog() {\n\n \/\/ calling parameterized constructor of the superclass\n super(\"Animal\");\n\n System.out.println(\"I am a dog\");\n }\n}\n\nclass Main {\n public static void main(String[] args) {\n Dog dog1 = new Dog();\n }\n}\n<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
Type: Animal\nI am a dog\n<\/samp><\/code><\/pre>\n\n\n\n
The compiler can automatically call the no-arg constructor. However, it cannot call parameterized constructors.<\/p>\n\n\n\n
If a parameterized constructor has to be called, we need to explicitly define it in the subclass constructor.<\/p>\n\n\n\n<\/figure>\n\n\n\n
Note that in the above example, we explicitly called the parameterized constructor super(\"Animal\")<\/code>. The compiler does not call the default constructor of the superclass in this case.<\/p>\n","protected":false},"excerpt":{"rendered":"
In this tutorial, we will learn about the super keyword in Java with the help of examples. The super keyword in Java is used in subclasses to access superclass members (attributes, constructors and methods). Before we learn about the\u00a0super\u00a0keyword, make sure to know about\u00a0Java inheritance. Uses of super keyword To call methods of the superclass that is […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[531],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1206"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=1206"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1206\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=1206"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=1206"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=1206"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"Java](\"https:\/\/cdn.programiz.com\/sites\/tutorial2program\/files\/java-overriding-example.png\")
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