Question

Java.
Must not use Java API java.util.Stack

/**
A class of stacks whose entries are stored in an array.
Implement all methods in ArrayStack class using resizable
array strategy, i.e. usedoubleArray()

Must throw StackException during exception events in methods:
   peek(), pop(), ArrayStack(int initialCapacity)
Do not change or add data fields
Do not add new methods

*/

import java.util.Arrays; public class Arraystack«Т> implements Stack!nterface«T> private TI stack;// Array of stack entries private int topIndex; /7 Index of top entry private static final int DEFAULT-CAPACITY = 50; / Construct a stack with DEFAULT_CAPACITY public ArrayStack() this (DEFAULTCAPACITY) > // end default constructor /* Construct a stack with the given initialCapacity * /* Throw StackException if initialCapacity0 public ArrayStack(int initialCapacity) // add stataments > // end constructor public void push(T newEntry) // add stataments // end push /* Throw StackException if stack is empty public T peek() // add stataments return null; > // end peek /* Throw StackException if stack is empty / public T pop() // add stataments return null; // end pop public boolean empty) // add stataments return false; // end empty public int size() // add stataments return 0; > // end size public void clear() // add stataments 1 // end clear /toString) returns a list of data in Stack, separate them with'' public String toString() // add stataments return null; // double the size of array using Arrays.copyof () private void doubleArray() // add stataments // end doubleArray public interface StackInterface T> /Gets the current number of data in this stack @return the integer number of entries currently in the stack* public int size); Adds a new data to the top of this stack. @param aData an object to be added to the stack / public void push (T aData); Removes and returns this stack's top data. @return the object at the top of the stack @throw StackException if the stack is empty* public T pop); / Retrieves this stack's top data. @return either the data at the top of the stack athrow StackException if the stack is empty public T peek); Detects whether this stack is empty @return true if the stack is empty */ public boolean empty) Removes all data from this stack public void clear) // end MyStackInterface public class StackException extends RuntimeException public StackException() this("" public StackException(String errorMsg) super(errorMsg);

Answer 1

public class ArrayStack<T> implements StackInterface<T> {

// Instance variables

private T[] stack; // Used to store the elements of this ArrayStack

private int topIndex; // Designates the first free cell

public static final int DEFAULT_CAPACITY = 50;

@SuppressWarnings("unchecked")

// Constructor

public ArrayStack(int capacity) {

if (capacity < DEFAULT_CAPACITY)

capacity = DEFAULT_CAPACITY;

stack = (T[]) new Object[capacity];

topIndex = 0;

}

// Returns true if this ArrayStack is empty

public boolean empty() {

// Same as:

// if ( top == 0 ) {

// return true;

// } else {

// return false;

// }

return (topIndex == 0);

}

// Returns the top element of this ArrayStack without removing it

public T peek() {

// pre-conditions: ! isEmpty()

if (empty())

return null;

return stack[topIndex - 1];

}

// Returns the 2nd top element of this ArrayStack without removing it

public T peek2() {

// pre-conditions: ! isEmpty()

if (empty() || topIndex - 2 < 0)

return null;

return stack[topIndex - 2];

}

// Removes and returns the top element of this stack

public T pop() {

// pre-conditions: ! isEmpty()

// pre-conditions: ! isEmpty()

if (empty())

return null;

if (topIndex < DEFAULT_CAPACITY) {

T[] temp = (T[]) new Object[topIndex];

for (int i = 0; i < topIndex; ++i) {

temp[i] = stack[i];

}

stack = temp;

}

// *first* decrements top, then access the value!

T saved = stack[--topIndex];

stack[topIndex] = null; // scrub the memory!

return saved;

}

// Puts the element onto the top of this stack.

public void push(Object element) {

// Pre-condition: the stack is not full

if (topIndex >= stack.length) {

T[] temp = (T[]) new Object[stack.length + DEFAULT_CAPACITY];

for (int i = 0; i < topIndex; ++i) {

temp[i] = stack[i];

}

stack = temp;

// *first* stores the element at position top, then increments top

stack[topIndex++] = (T) element;

} else {

// *first* stores the element at position top, then increments top

stack[topIndex++] = (T) element;

}

}

public String toString() {

String res = "";

for (int i = topIndex - 1; i >= 0; --i)

res = res + stack[i] + " ";

return res;

}

public T[] reverse() {

Object ob[] = new Object[topIndex];

for (int i = topIndex - 1; i >= 0; --i)

ob[i] = stack[i];

return (T[]) ob;

}

public boolean search(T p) {

Object ob[] = new Object[topIndex];

for (int i = topIndex - 1; i >= 0; --i)

if (stack[i].equals(p))

return true;

return false;

}

public boolean isFull() {

// TODO Auto-generated method stub

return topIndex >= stack.length;

}

public static void main(String args[]) {

ArrayStack<Integer> as = new ArrayStack<Integer>(26);

as.push(10);

as.push(20);

as.push(30);

as.push(10);

as.push(60);

as.push(70);

as.push(10);

as.pop();

as.pop();

as.pop();

System.out.println("Method Peek returns : " + as.peek());

as.push(10);

as.push(60);

as.push(70);

System.out.println(as.toString());

}

@Override

public int size() {

// TODO Auto-generated method stub

return topIndex;

}

@Override

public void clear() {

// TODO Auto-generated method stub

stack = null;

topIndex = 0;

}

}

=========================================
SEE output


152 public static void main(String args ArrayStack<Integer> as -new ArrayStack<Integer>(26); as.push(10); as.push(20); as.push(30); as.push(10); as.push(60); as.push(70); as.push(10); as.popC; as.pop); as.pop); System.out.println"Method Peek returns" as.peekDD as.push(10); as.push (60); as.push(70); System. out.println(as.toStringO); 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 E Console 3 <terminated> ArrayStack (1) [Java Application] /Library/Java/JavaVirtualMachines/jdk1.8.0 202.jdk/Contents/H Method Peek returns: 10 70 60 10 10 30 20 10


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