Question

Can someone help me to figure that error I have put below. JAVA

----jGRASP exec: javac -g P4Program.java
P4Program.java:94: error: package list does not exist
Iterator i = new list.iterator();
^
1 error

----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.

Note: Below there are two different classes that work together. Each class has it's own fuctions/methods.

import java.util.*;
import java.io.*;

public class P4Program{

public void linkedStackFromFile(){

String content = new String();
int count = 1;
File file = new File("P4Input.txt");
LinkedStack<String> list = new LinkedStack<String>();

try {
Scanner sc = new Scanner(new FileInputStream(file));
while (sc.hasNextLine()){
content = sc.nextLine();
list.push(content);
}
sc.close();
}catch(FileNotFoundException fnf){
fnf.printStackTrace();
}
catch (Exception e) {
e.printStackTrace();
System.out.println("\nProgram terminated Safely...");
}
Iterator i = new list.iterator();
while (i.hasNext()) {
System.out.print("Node " + (count++) + " : ");
System.out.println(i.next());
}
}

public static void main (String [] arg)throws IOException{

P4Program mainClass = new P4Program();
  
mainClass.linkedStackFromFile();
}
}

----jGRASP exec: javac -g P4Program.java
P4Program.java:94: error: package list does not exist
Iterator i = new list.iterator();
^
1 error

----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.

import java.io.*;
import java.util.*;

public class LinkedStack<Item>{
private int n; // size of the stack
private Node first; // top of stack

// helper linked list class
private class Node {
private Item item;
private Node next;
}

/**
* Initializes an empty stack.
*/
public LinkedStack() {
first = null;
n = 0;
}

/**
* Is this stack empty?
* @return true if this stack is empty; false otherwise
*/
public boolean isEmpty() {
return first == null;
}

/**
* Returns the number of items in the stack.
* @return the number of items in the stack
*/
public int size() {
return n;
}

/**
* Adds the item to this stack.
* @param item the item to add
*/
public void push(Item item) {
Node oldfirst = first;
first = new Node();
first.item = item;
first.next = oldfirst;
n++;
}

/**
* Removes and returns the item most recently added to this stack.
* @return the item most recently added
* @throws java.util.NoSuchElementException if this stack is empty
*/
public Item pop() {
if (isEmpty()) throw new NoSuchElementException("Stack underflow");
Item item = first.item; // save item to return
first = first.next; // delete first node
n--;
return item; // return the saved item
}
}

Answer 1

$Use \;temporary \;variable(temp) \;to \;loop \;through \;the \;list.\;$

$\color{blue}\underline{P4Program.java:}$

import java.util.*;
import java.io.*;

public class P4Program{

    public void linkedStackFromFile(){

        String content = new String();
        int count = 1;
        File file = new File("P4Input.txt");
        LinkedStack<String> list = new LinkedStack<String>();

        try {
            Scanner sc = new Scanner(new FileInputStream(file));
            while (sc.hasNextLine()){
                content = sc.nextLine();
                list.push(content);
            }
            sc.close();
        }catch(FileNotFoundException fnf){
            fnf.printStackTrace();
        }
        catch (Exception e) {
            e.printStackTrace();
            System.out.println("\nProgram terminated Safely...");
        }

        LinkedStack<String> temp = list;
        while (!temp.isEmpty()) {
            System.out.print("Node " + (count++) + " : ");
            System.out.println(temp.pop());
        }
    }

    public static void main (String [] arg)throws IOException{

        P4Program mainClass = new P4Program();

        mainClass.linkedStackFromFile();
    }
}

$\color{blue}\underline{LinkedStack.java:}$

import java.io.*;
import java.util.*;


public class LinkedStack<Item>{
    private int n;          // size of the stack
    private Node first;     // top of stack

    // helper linked list class
    private class Node {
        private Item item;
        private Node next;
    }

    /**
     * Initializes an empty stack.
     */
    public LinkedStack() {
        first = null;
        n = 0;
    }

    /**
     * Is this stack empty?
     * @return true if this stack is empty; false otherwise
     */
    public boolean isEmpty() {
        return first == null;
    }

    /**
     * Returns the number of items in the stack.
     * @return the number of items in the stack
     */
    public int size() {
        return n;
    }

    /**
     * Adds the item to this stack.
     * @param item the item to add
     */
    public void push(Item item) {
        Node oldfirst = first;
        first = new Node();
        first.item = item;
        first.next = oldfirst;
        n++;
    }

    /**
     * Removes and returns the item most recently added to this stack.
     * @return the item most recently added
     * @throws java.util.NoSuchElementException if this stack is empty
     */
    public Item pop() {
        if (isEmpty()) throw new NoSuchElementException("Stack underflow");
        Item item = first.item;        // save item to return
        first = first.next;            // delete first node
        n--;
        return item;                   // return the saved item
    }
}

$\color{blue}\underline{P4Input.txt:}$

ABC
DEF
GHI

$\color{red}\underline{Output:}$

Node 1:GHI Node 2 DEF Node 3 ABC Process finished with exit code 0

$\color{red}NOTE: \;If \;you \;have \;any \;doubts \;in \;this \;solution, \;Please \;comment \;below.\;$