How to use super in java

super is the keyword used to access super class members in Java. The specific usage is: calling the method in the super class: super.method_name() accessing the variable in the super class: super.variable_name calling the super class Constructor: super(arguments)

Usage of super in Java

What is super?

super is a keyword in Java used to access members of a super class. It refers to the immediate superclass of the class that calls it.

Usage of super

There are three main uses of super:

• Access methods in the super class: super .method_name() will call the method named method_name in the superclass.
• Accessing variables in a superclass: super.variable_name will refer to a variable named variable_name in the superclass.
• Call the constructor of the super class: super(arguments) will call the constructor of the super class, passing the given parameters.

When to use super

Common situations where super is used include:

• Override method: When a subclass needs to override a method in the superclass, super.method_name() can be used to call the overridden method.
• Using variables or methods of the superclass: When a subclass needs to access variables or methods in the superclass, but they are not available in the subclass.
• Call the constructor of the super class: When the subclass needs to initialize the state of the super class.

Example

class SuperClass {
    int value = 10;
    void printValue() {
        System.out.println("SuperClass value: " + value);
    }
}

class SubClass extends SuperClass {
    int value = 20;
    @Override
    void printValue() {
        super.printValue(); // 调用超类中的 printValue 方法
        System.out.println("SubClass value: " + value);
    }
}

public class Main {
    public static void main(String[] args) {
        SubClass obj = new SubClass();
        obj.printValue(); // 输出：
                            // SuperClass value: 10
                            // SubClass value: 20
    }
}

Note:

• super can only be used in methods of subclasses .
• If the superclass does not have a method named method_name, super.method_name() will cause a compilation error.
• super cannot be used to access members in the parent interface.
• super cannot be used to access private members of the parent class.

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