Java Super-class Constructors .
Java Super-class Constructors
- A constructor can invoke a super-class constructor using the method call super().
- You must support the super() method with appropriate arguments to select the desired super-class constructor.
- The special call to super() must appear as the first statement in your delegating constructor.
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Making super() call to a super-class constructors from other methods is illegal.
Super-class Constructor example:
class Person { private int age; private String name; public Person(int age, String name) { this.age = age; this.name = name; } @Override public String toString() { return ("My name is " + name + " and I am " + age + " years old."); } } class Doctor extends Person { private String specialty; Doctor(int age, String name, String specialty) { // This is a call to the Person constructor with two parameters super(age, name); this.specialty = specialty; } @Override public String toString() { return super.toString() + " My profession is " + specialty; } } public class SuperDemo { public static void main(String args[]) { Person peter = new Person(45, "Peter"); System.out.println(peter); Doctor fred = new Doctor(46, "Fred", "dermatologist"); System.out.println(fred); } }
The result of this is:My name is Peter and I am 45 years old. My name is Fred and I am 46 years old. My profession is dermatologist
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