hello.. i really need help.. I don't know why i keep on getting an empty stack if i pop a token from stack even if user has already push a token into it..
public class MStack implements Stack{
public Node top;
public Node[] stack;
public static int T[];
public static int B[];
public static int oldT[];
public static int i;
int size2;
int noOfStack;
class Node{
Object info;
Node link;
}
public MStack(){
}
public MStack(int size, int noOfStack){
size2= size;
stack = new Node[size];
T = new int[noOfStack + 1];
B = new int[noOfStack + 1];
for (int i = 0; i < noOfStack+1; i++){
B[i]= (int)Math.floor(size/noOfStack) * i -1;
T[i] = B[i];
}
}
public Object top(int i){
if (isEmpty(i)){
System.out.println("Stack empty.");
}return top.info;
}
public void push(String item,int i ) {
if (T[i]== B[i+1]){
System.out.println("Stack"+ i + "is full.");
}else{
Node newNode = new Node();
newNode.info = item;
newNode.link = top;
top = newNode;
System.out.println("You have pushed an element into stack");
}
}
public Object pop(int i ){
Node temp[] = new Node[noOfStack];
if (isEmpty(i)){
System.out.println("Stack has nothing inside it");
}
temp[i] = top;
top = top.link;
return temp[i].info;
}
public boolean isEmpty(int i){
return (T[i] == B[i]);
}
public int size(int i){
int size = T[i] - B[i] ;
return size;
}
}
this is another class. This has the main type:
import java.io.*;
public class BookShelf extends MStack {
public static InputStreamReader ir = new InputStreamReader(System.in);
public static BufferedReader bf = new BufferedReader(ir);
public static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
public static MStack bookShelf;
public static int size;
public static int shelf;
public static void main (String []args) throws IOException{
System.out.println("What size do you want your bookshelf to be?(integer):");
size = Integer.parseInt(in.readLine());
System.out.println("How many shelves do you want your bookshelf to have?:");
shelf = Integer.parseInt(in.readLine());
bookShelf = new MStack(size, shelf);
new BookShelf();
}
public BookShelf(){
super();
options();
}
public void options(){
try{
do{
System.out.println("\nPlease choose from below. Use numbers to choose.");
System.out.println("1. Place book on shelf");
System.out.println("2. Retrieve book from shelf");
System.out.println("3. View books on each shelf");
System.out.println("4. Exit");
int choice = Integer.parseInt(in.readLine());
if (choice == 1){
System.out.println("Which shelf do you want to place a book?");
System.out.println("Enter either 1, 2 or 3");
int placement = Integer.parseInt(in.readLine());
if(placement == 1){
System.out.println("Enter element:");
String item = bf.readLine();
garwick(placement);
bookShelf.push(item, placement);
}if(placement == 2){
System.out.println("Enter an element:");
String item = bf.readLine();
garwick(placement);
bookShelf.push(item, placement);
}if(placement == 3){
System.out.println("Enter an element:");
String item = bf.readLine();
garwick(placement);
bookShelf.push(item, placement);
}
}else if (choice == 2){
System.out.println("Which shelf do you want to retrieve a book, 1, 2, or 3?");
int choice2 = Integer.parseInt(in.readLine());
switch (choice2){
case 1 : if (bookShelf.isEmpty(choice2)) {
System.out.println( " Shelf " + choice2 + " is empty!");
}else {
System.out.println("Item" + bookShelf.pop(choice2)+ " is retrieved.");
}break;
case 2 : if (bookShelf.isEmpty(choice2)) {
System.out.println(" Shelf " + choice2 + " is empty!");
}else {
System.out.println("Item" + bookShelf.pop(choice2)+ " is retrieved.");
}break;
case 3 : if (bookShelf.isEmpty(choice2)) {
System.out.println(" Shelf " + choice2 + " is empty!");
}else {
System.out.println("Item" + bookShelf.pop(choice2)+ " is retrieved.");
}break;
}
}else if(choice == 3){
System.out.println("Recent items");
for (int i = 1; i <= shelf; ++i) {
System.out.println("shelf #" + i + ": " + bookShelf.top(i));
}
System.out.println("shelf #" + i + ": Empty");
}else if (choice == 4){
System.out.println("You have exited. Thank you!");
break;
}
}while (true);
}catch(IOException e){}
}
/*
* Method that implements garwick's algorithm for reallocating free space
* within a multiple stack
*/
public void garwick(int i) {
int diff[] = new int[shelf + 1];
int size[] = new int[shelf + 1];
int totalSize = 0;
double freecells, incr = 0;
double alpha, beta, sigma = 0, tau = 0;
/* Compute for the allocation factors */
for (int j = 1; j <= bookShelf.noOfStack; j++) {
size[j] = bookShelf.size(j);
if ((bookShelf.T[j] - bookShelf.oldT[j]) > 0){
diff[j] = bookShelf.T[j] - bookShelf.oldT[j];
}else{
diff[j] = 0;
totalSize += size[j];
incr += diff[j];
}
}
diff[i]++;
size[i]++;
totalSize++;
incr++;
freecells = bookShelf.size2 - totalSize;
alpha = 0.10 * freecells / bookShelf.noOfStack;
beta = 0.90 * freecells / incr;
/* If all stacks are full */
if (freecells < 1)
throw new StackException("Stack overflow: All Stacks are full");
/* Compute for new bases */
for (int j = 2; j <= bookShelf.noOfStack; j++) {
tau = sigma + alpha + diff[j - 1] * beta;
bookShelf.B[j] = bookShelf.B[j - 1] + size[j - 1] + (int) Math.floor(tau)- (int) Math.floor(sigma);
sigma = tau;
}
/* Restore size of the overflowed stack to its old value */
size[i]--;
System.out.println("size[" + i + "] = " + size[i]);
/* Compute for new top addresses */
for (int j = 1; j <= bookShelf.noOfStack; j++) {
bookShelf.T[j] = bookShelf.B[j] + size[j];
}
bookShelf.oldT = bookShelf.T;
}
}
It implements the Stack interface.
I run this on eclipse compiler.
Can someone help me please.. thanks a lot.. i really need to finish this asap..
