Turn stack into a string?

Question

I'm working on a project for class and we need to create a method that takes the stack we created and when called print itself out as a string. This is what I have so far; the method is at the bottom called toString();.

package edy.bsu.cs121.stack;

import javax.swing.JOptionPane;

public class myArrayStack<T> {

    private final int DEFAULT_CAPACITY = 100;
    private int top;
    private T[] stack;

    @SuppressWarnings("unchecked")
    public myArrayStack(){

        top = 0;
        stack = (T[])(new Object[DEFAULT_CAPACITY]);
    
    }

    @SuppressWarnings("unchecked")
    public myArrayStack(int initialCapacity){
     
        top = 0;
        stack = (T[])(new Object[initialCapacity]);
            
    }

    public void myPush(String first){
    
        stack[top] = (T) first;
        top++;
    }

    public T myPop(){
    
        if (isEmpty()){
            JOptionPane.showMessageDialog(null, "Stack is empty!");
        } else {
            top--;
        }
        T result = stack[top];
        stack[top] = null;
        return result;
    }

    public T myPeek(){
        if (isEmpty()){
            JOptionPane.showMessageDialog(null, "Stack is empty!");
        }
        return stack[top-1];
    }

    public boolean isEmpty(){
    
        if (top == 0){
            return true;    
        }
    
        return false;
    }

    public int mySize(){
        return top;
    }

    //Searches for a name

    public int mySearch (T element) {
    {   
        int spot = -1;
        for(int i = 0; i< top; i ++){
            if(element.equals(stack[i])){
                spot = i;
            } 
        }
        return spot;
    }
    }

    public String toString(){
        int i=top;
    
        do {
            T result = stack[top-i];
            i--;
            return (String) result;
        } while (i>=0);
    
    }

}

the toString method will only return the top item in the Stack; the loop won't run through the whole stack like I need it to. — user2514769
– user2514769, Commented Jun 24, 2013 at 2:45
You pop each element out your stack and call to string. Read more about to string in tutorialspoint.com/java/number_tostring.htm — dev2d
– dev2d, Commented Jun 24, 2013 at 2:51

NCVolt · Accepted Answer · 2023-01-08 21:20:49Z

2

Using Stream API:

Stack<Character> st = new Stack<>();
st.add('a');st.add('b');st.add('c');

String stStr = st.stream().map(s -> s.toString()).collect(Collectors.joining(""));

System.out.println(stStr);

answered Jan 8, 2023 at 21:20

NCVolt

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Comments

Martin Wickham · Accepted Answer · 2013-06-24 03:03:12Z

0

Calling return in a loop will immediately exit the loop. What you need to do is something like this:

String message = ""; //a string to store the whole message
for (int c = stack.length - 1; c >= 0; c--) {
  message += ", "+stack[c];  //add the next element to the message
}
message = message.substring(2); //cut off the first ", "
return message;

answered Jun 24, 2013 at 3:03

Martin Wickham

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Comments

BevynQ · Accepted Answer · 2013-06-24 03:00:54Z

0

Use a StringBuilder to handle the toString creation. A template you could use is

public String toString(){
    StringBuilder output = new StringBuilder();
    output.append(this.getClass().getName());
    output.append("[");
    // append fields

    // to append the Stack you could use Arrays.toString
    // or just iterate as you are trying to do
    int i=top;

    do {
        T result = stack[top-i];
        i--;
        output.append(result != null?result.toString():"null");
    } while (i>=0);

    output.append("]");
    return output.toString();
}

answered Jun 24, 2013 at 3:00

BevynQ

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Comments

Shalom Alexander · Accepted Answer · 2024-09-18 16:46:22Z

0

The intuitive way is to use a combination of Stream API + StringBuilder.

Stream API + StringBuilder

StringBuilder sb = new StringBuilder("");
stack.stream().forEach(c -> sb.append(c)); // iterates from bottom to top of stack
System.out.println(sb.toString());

answered Sep 18, 2024 at 16:46

Shalom Alexander

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Comments

Alexey Bril · Accepted Answer · 2025-03-03 20:47:22Z

0

Java 11+. ArrayDeque. Stream API.

public static void main(String[] args) {
    System.out.println(execute("azxxzy"));
}

public static String execute(String s) {
    Deque<Character> stack = new ArrayDeque<>();
    for (Character c : s.toCharArray()) {
        stack.addLast(c);
    }

    return stack.stream().map(Object::toString).collect(Collectors.joining());
}

output: azxxzy

answered Mar 3 at 20:47

Alexey Bril

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