How can we do the same piece of code in the single file

#1

as it is written there in two different files and executed ,unlike that way how can we write it in single file.

#2

yes we write this.
i have written this code below

hope this will help u
pls rate my work so that i can improve my work

import java.util.*;

public class linkedlist {

private class Node {
	int data;
	Node next;
}

private Node head;
private Node tail;
private int size;

public void display() {
	Node temp = head;
	for (int i = 0; i < size; i++) {
		System.out.print(temp.data + " ");
		temp = temp.next;
	}
	System.out.println();
}

public int size() {
	return size;
}

public void handlezerosize(int data) {
	Node nn = new Node();
	nn.data = data;
	nn.next = null;
	tail = nn;
	head = nn;
	size = 1;
}



public void addlast(int data) {
	if (size == 0)
		handlezerosize(data);
	else {
		Node nn = new Node();
		nn.data = data;
		nn.next = null;
		tail.next = nn;
		tail = nn;
		size++;
	}
}
    public static void main(String args[]) {
    	linkedlist l=new linkedlist();
    	l.addlast(5);
    	l.addlast(7);
    	l.addlast(8);
    	l.addlast(6);
    	l.display();
    }  
    }