In your lab05, replace instructor’s Tokenizer class and MyStackQueue package with your own.

[duster bask]

Objective:

The objective of this lab is to get you some experience in processing strings character by
character and in implementing stacks and queues in a class package.

The programming assignment:
In your lab05, replace instructor’s Tokenizer class and MyStackQueue package with your own.

Requirements:
1. You must use an array to implement your queue.
2. You must use a linked list to implement your stack.
3. You must use the following frame work to implement your tokenizer.
class Tokenizer {
private char [] Buf;
private int cur;
Tokenizer(String infixExpression) {
Buf = infixExpression.toCharArray();
cur = 0;
}
Token nextToken() {
1. Skip blanks.

2. if (cur>=Buf.length) return null;

3. If the next character is a digit, keep reading until a non-digit is read.

Convert the string of digits into an integer.
String Digits = new String(Buf, start, len);
int num = Integer.valueOf(Digits).intValue();
Create and return an operand.
4. Otherwise, use the next character to create and return an operator.
}
}


I have developed these classes is it correct?


package StackAndQueue;

import java.util.LinkedList;
import java.util.List;

public class Stack {

	List<Object> linkedList = null;

	public Stack() {
		linkedList = new LinkedList<Object>();
	}

	public boolean isEmpty() {
		return linkedList.size() == 0;
	}

	public void push(Object obj) {
		linkedList.add(obj);
	}

	public Object pop() {
		int topIndex = linkedList.size() - 1;
		if (topIndex >= 0) {
			Object obj = linkedList.get(topIndex);
			linkedList.remove(topIndex);
			return obj;
		} else {
			return null;
		}
	}

	public Object top() {
		int topIndex = linkedList.size() - 1;
		if (topIndex >= 0) {
			return linkedList.get(topIndex);
		} else {
			return null;
		}
	}
}

package StackAndQueue;

public class Queue {

	private int front;
	private int rear;
	private int capacity;
	private Object S[];

	public Queue() {
		front = 0;
		rear = -1;
		capacity = 100;
		S = new Object[capacity];
	}

	public boolean isEmpty() {
		return S[front] == null;
	}

	public void enqueue(Object obj) {
		int insertionPoint = (rear + 1) % capacity;
		if (S[insertionPoint] == null) {
			S[insertionPoint] = obj;
			rear = insertionPoint;
		} else {
			System.out.println("Queue capacity is full");
		}
	}

	public Object dequeue() {
		if (S[front] != null) {
			Object obj = S[front];
			S[front] = null;
			front = (front + 1) % capacity;
			return obj;
		} else {
			System.out.println("Queue is empty");
			return null;
		}
	}

	public String toString() {
		StringBuilder state = new StringBuilder("[");
		for (int i = front; i < capacity; i++) {
			if (S[i] != null) {
				state.append(S[i] + ", ");
			}
		}
		for (int i = 0; i < front; i++) {
			if (S[i] != null) {
				state.append(S[i] + ", ");
			}
		}
		if (state.length() > 1) {
			state.delete(state.length() - 2, state.length() - 1);
		}
		state.append("]");
		return state.toString();
	}
}

class Tokenizer {
	private char[] Buf;
	private int cur;

	Tokenizer(String infixExpression) {
		Buf = infixExpression.toCharArray();
		cur = 0;
	}

	Token nextToken() {
		int bufLength = Buf.length;
		Object obj = null;
		// ignore blank space
		while (cur < bufLength && Buf[cur] == ' ') {
			cur++;
		}

		// if given string having only space return null
		if (cur >= Buf.length)
			return null;

		StringBuilder value = new StringBuilder();
		// Iterate through each element of string array and construct an string
		// for consecutive digits
		while (cur < bufLength && Buf[cur] <= '9' && Buf[cur] >= '0') {
			value.append(Buf[cur]);
			cur++;
		}
		// if digits are there convert all digits as an integer value and create
		// operand
		if (value.length() > 0) {
			obj = new Operand(Integer.parseInt(value.toString()));
		}
		// if at cur position no digit is present then create operand with the
		// same non digit value
		else {
			obj = new Operator(Buf[cur]);
			cur++;
		}
		return ((Token) (obj));
	}

}

[Jeff Verdegan]

Hi, and welcome to the Ranch!

Before we get started, there are a few things you should know.

First, you need to TellTheDetails(←click). We can't help you if you're not clear and specific about what problem you're having. As for your question, "Is it correct?" only your instructor can answer that for sure, because only he knows what he's looking for. You can and should run your code with some test data to see if it does what the assignment says it should. If it does, there's a good chance it's correct, or at least mostly so. If not, then you still have work to do.

Additionally, when posting code, please UseCodeTags(←click) so that it will be readable. You can edit your original post and add them.

Thanks, and good luck!

[fred rosenberger]

Here is your code with the proper tags. See how much better it looks?

package StackAndQueue;

import java.util.LinkedList;
import java.util.List;

public class Stack {

	List<Object> linkedList = null;

	public Stack() {
		linkedList = new LinkedList<Object>();
	}

	public boolean isEmpty() {
		return linkedList.size() == 0;
	}

	public void push(Object obj) {
		linkedList.add(obj);
	}

	public Object pop() {
		int topIndex = linkedList.size() - 1;
		if (topIndex >= 0) {
			Object obj = linkedList.get(topIndex);
			linkedList.remove(topIndex);
			return obj;
		} else {
			return null;
		}
	}

	public Object top() {
		int topIndex = linkedList.size() - 1;
		if (topIndex >= 0) {
			return linkedList.get(topIndex);
		} else {
			return null;
		}
	}
}


package StackAndQueue;

public class Queue {

	private int front;
	private int rear;
	private int capacity;
	private Object S[];

	public Queue() {
		front = 0;
		rear = -1;
		capacity = 100;
		S = new Object[capacity];
	}

	public boolean isEmpty() {
		return S[front] == null;
	}

	public void enqueue(Object obj) {
		int insertionPoint = (rear + 1) % capacity;
		if (S[insertionPoint] == null) {
			S[insertionPoint] = obj;
			rear = insertionPoint;
		} else {
			System.out.println("Queue capacity is full");
		}
	}

	public Object dequeue() {
		if (S[front] != null) {
			Object obj = S[front];
			S[front] = null;
			front = (front + 1) % capacity;
			return obj;
		} else {
			System.out.println("Queue is empty");
			return null;
		}
	}

	public String toString() {
		StringBuilder state = new StringBuilder("[");
		for (int i = front; i < capacity; i++) {
			if (S[i] != null) {
				state.append(S[i] + ", ");
			}
		}
		for (int i = 0; i < front; i++) {
			if (S[i] != null) {
				state.append(S[i] + ", ");
			}
		}
		if (state.length() > 1) {
			state.delete(state.length() - 2, state.length() - 1);
		}
		state.append("]");
		return state.toString();
	}
}

class Tokenizer {
	private char[] Buf;
	private int cur;

	Tokenizer(String infixExpression) {
		Buf = infixExpression.toCharArray();
		cur = 0;
	}

	Token nextToken() {
		int bufLength = Buf.length;
		Object obj = null;
		// ignore blank space
		while (cur < bufLength && Buf[cur] == ' ') {
			cur++;
		}

		// if given string having only space return null
		if (cur >= Buf.length)
			return null;

		StringBuilder value = new StringBuilder();
		// Iterate through each element of string array and construct an string
		// for consecutive digits
		while (cur < bufLength && Buf[cur] <= '9' && Buf[cur] >= '0') {
			value.append(Buf[cur]);
			cur++;
		}
		// if digits are there convert all digits as an integer value and create
		// operand
		if (value.length() > 0) {
			obj = new Operand(Integer.parseInt(value.toString()));
		}
		// if at cur position no digit is present then create operand with the
		// same non digit value
		else {
			obj = new Operator(Buf[cur]);
			cur++;
		}
		return ((Token) (obj));
	}

}

[duster bask]

Thank you very much for help, Actually I wanted to know my coding is correct or there are some logical errors.

[Jeff Verdegan]

duster bask wrote:Thank you very much for help, Actually I wanted to know my coding is correct or there are some logical errors.

As I said in my first reply: As for your question, "Is it correct?" only your instructor can answer that for sure, because only he knows what he's looking for. You can and should run your code with some test data to see if it does what the assignment says it should. If it does, there's a good chance it's correct, or at least mostly so. If not, then you still have work to do.

So, test it.