Extend a java class from one file in another java file

How can I include one java file into another java file?

For example: If I have 2 java file one is called Person.java and one is called Student.java. How can I include Person.java into Student.java so that I can extend the class from Person.java in Student.java

Solution 1:

Just put the two files in the same directory. Here's an example:

Person.java

public class Person {
  public String name;

  public Person(String name) {
    this.name = name;
  }

  public String toString() {
    return name;
  }
}

Student.java

public class Student extends Person {
  public String somethingnew;

  public Student(String name) {
    super(name);
    somethingnew = "surprise!";
  }

  public String toString() {
    return super.toString() + "\t" + somethingnew;
  }

  public static void main(String[] args) {
    Person you = new Person("foo");
    Student me = new Student("boo");

    System.out.println("Your name is " + you);
    System.out.println("My name is " + me);
  }
}

Running Student (since it has the main function) yields us the desired outcome:

Your name is foo
My name is boo  surprise!

Solution 2:

What's missing from all the explanations is the fact that Java has a strict rule of class name = file name. Meaning if you have a class "Person", is must be in a file named "Person.java". Therefore, if one class tries to access "Person" the filename is not necessary, because it has got to be "Person.java".

Coming for C/C++, I have exact same issue. The answer is to create a new class (in a new file matching class name) and create a public string. This will be your "header" file. Then use that in your main file by using "extends" keyword.

Here is your answer:

1. Create a file called Include.java. In this file, add this:

   public class Include {
       public static String MyLongString= "abcdef";
   }
   

2. Create another file, say, User.java. In this file, put:

   import java.io.*;
   
   public class User extends Include {
       System.out.println(Include.MyLongString);
   }