Question

I get an error when im trying to run this java program, I would appreciate if someone helped me asap, I will make sure to leave a good review. thank you in advance!

java class Node

public class Node {
private char item;
private Node next;
Object getNext;

public Node(){
  
item = ' ';
next = null;
}
public Node(char newItem) {
setItem(newItem);
next = null;
}
public Node(char newItem, Node newNext){
setItem(newItem);
setNext(newNext);
}
public void setItem(char newItem){
item = newItem;
}
public void setNext(Node newNext){
next = newNext;
}
public char getItem(){
return item;
}
public Node getNext(){
return next;
}
  
}

java class LinkedString

public class LinkedString {
Node head;
int length;
  
public LinkedString(char[] characters) {

for(int i=0;i<characters.length;i++) {
Node newNode = new Node(characters[i]);
if(head==null) {
head = newNode;
}
else
{
Node curr=head;
while(curr.getNext!=null)
{
curr=curr.getNext();
}
curr = newNode;
}
}
length=characters.length;
}
public LinkedString(String str) {
for(int i=0;i<str.length();i++) {
Node newNode = new Node(str.charAt(i));
if(head==null) {
head = newNode;
}
else
{
Node curr=head;
while(curr.getNext!=null)
{
curr=curr.getNext();
}
curr = newNode;
}
}
length=str.length();
}
  
public char charAt(int index)
{
Node curr;
curr = head;
if (index == 0){
return curr.getItem();
}else if(index > 0 && index < length){
for (int i = 1; i<index; i++){
curr = curr.getNext();
}
}
return 0;

}
  

public LinkedString concat(LinkedString str)
{
if(isEmpty())
{
length=str.length();
return str;
}
Node curr=head;
while(curr.getNext!=null)
{
curr = curr.getNext();
}
curr.setNext(str.head);
length=length+str.length();
return this;
}
  
public boolean isEmpty() {
return length==0;
}
  
public int length() {
return length;
}
  
public LinkedString replace(char oldChar,char newChar) {
Node curr = head;
while(curr!=null) {
if(curr.getItem()==oldChar)
curr.setItem(newChar);
curr = curr.getNext();
}
  
return this;
}
  

public String toString() {
Node curr = head;
String ans = "";
while(curr!=null) {
ans+=curr.getItem();
curr = curr.getNext();
}
return ans;
}   

}

java class test

public class Test {


public static void main(String[] args) {
char array[]= {'m','a','h','d','i'};
System.out.println("String 1: ");
LinkedString LS1=new LinkedString(array);
System.out.println("isEmpty: "+LS1.isEmpty());
System.out.println("Length :"+LS1.length());
System.out.println("String form: "+LS1.toString());
System.out.println("Character At index 3: "+LS1.charAt(3));
  
System.out.println("\nlinkedString Object 2: ");
LinkedString LS2=new LinkedString("mazloumi");
System.out.println("isEmpty: "+LS2.isEmpty());
System.out.println("Length :"+LS2.length());
System.out.println("String form: "+LS2.toString());
System.out.println("Character At index 5: "+LS2.charAt(5));
  
  
System.out.println("\nConcatenated linked String: ");
LinkedString LS3=LS1.concat(LS2);
System.out.println("isEmpty: "+LS3.isEmpty());
System.out.println("Length :"+LS3.length());
System.out.println("String form: "+LS3.toString());
System.out.println("Character At index 10: "+LS3.charAt(10));

  
System.out.println("\nReplaced String: ");
LinkedString ls4=LS3.replace('a', 'o');
System.out.println(ls4.toString());
}

}

Answer 1

class Node {
        private char item;
        private Node next;
        Object getNext;

        public Node() {

                item = ' ';
                next = null;
        }

        public Node(char newItem) {
                setItem(newItem);
                next = null;
        }

        public Node(char newItem, Node newNext) {
                setItem(newItem);
                setNext(newNext);
        }

        public void setItem(char newItem) {
                item = newItem;
        }

        public void setNext(Node newNext) {
                next = newNext;
        }

        public char getItem() {
                return item;
        }

        public Node getNext() {
                return next;
        }

}

class LinkedString {
        Node head;
        int length;

        public LinkedString(char[] characters) {

                for (int i = 0; i < characters.length; i++) {
                        Node newNode = new Node(characters[i]);
                        if (head == null) {
                                head = newNode;
                        } else {
                                Node curr = head;
                                while (curr.getNext != null) {
                                        curr = curr.getNext();
                                }
                                curr = newNode;
                        }
                }
                length = characters.length;
        }

        public LinkedString(String str) {
                for (int i = 0; i < str.length(); i++) {
                        Node newNode = new Node(str.charAt(i));
                        if (head == null) {
                                head = newNode;
                        } else {
                                Node curr = head;
                                while (curr.getNext != null) {
                                        curr = curr.getNext();
                                }
                                curr = newNode;
                        }
                }
                length = str.length();
        }

        public char charAt(int index) {
                Node curr;
                curr = head;
                if (index == 0) {
                        return curr.getItem();
                } else if (index > 0 && index < length) {
                        for (int i = 1; i < index; i++) {
                                //added null check before caling getNext()
                                if(curr!=null)
                                curr = curr.getNext();
                        }
                }
                return 0;

        }

        public LinkedString concat(LinkedString str) {
                if (isEmpty()) {
                        length = str.length();
                        return str;
                }
                Node curr = head;
                while (curr.getNext != null) {
                        curr = curr.getNext();
                }
                curr.setNext(str.head);
                length = length + str.length();
                return this;
        }

        public boolean isEmpty() {
                return length == 0;
        }

        public int length() {
                return length;
        }

        public LinkedString replace(char oldChar, char newChar) {
                Node curr = head;
                while (curr != null) {
                        if (curr.getItem() == oldChar)
                                curr.setItem(newChar);
                        curr = curr.getNext();
                }

                return this;
        }

        public String toString() {
                Node curr = head;
                String ans = "";
                while (curr != null) {
                        ans += curr.getItem();
                        curr = curr.getNext();
                }
                return ans;
        }

}

public class TestLin {

        public static void main(String[] args) {
                char array[] = { 'm', 'a', 'h', 'd', 'i' };
                System.out.println("String 1: ");
                LinkedString LS1 = new LinkedString(array);
                System.out.println("isEmpty: " + LS1.isEmpty());
                System.out.println("Length :" + LS1.length());
                System.out.println("String form: " + LS1.toString());
                System.out.println("Character At index 3: " + LS1.charAt(3));

                System.out.println("\nlinkedString Object 2: ");
                LinkedString LS2 = new LinkedString("mazloumi");
                System.out.println("isEmpty: " + LS2.isEmpty());
                System.out.println("Length :" + LS2.length());
                System.out.println("String form: " + LS2.toString());
                System.out.println("Character At index 5: " + LS2.charAt(5));

                System.out.println("\nConcatenated linked String: ");
                LinkedString LS3 = LS1.concat(LS2);
                System.out.println("isEmpty: " + LS3.isEmpty());
                System.out.println("Length :" + LS3.length());
                System.out.println("String form: " + LS3.toString());
                System.out.println("Character At index 10: " + LS3.charAt(10));

                System.out.println("\nReplaced String: ");
                LinkedString ls4 = LS3.replace('a', 'o');
                System.out.println(ls4.toString());
        }

}

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