Thread: Hi guys, can any one tell what's wrong with my code?This is about stack as arrays and this is based on bluej environment

import java.io.*;
public class StackImplementation
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int max;
int top;
int stack[];

public StackImplementation()
{
top=0;
max=0;
stack=new int[max];
}

public void Push(int num)
{
System.out.println("Top: "+top+"and max: "+max);
if(top==max)
System.out.println("STACK OVERFLOW!!!");
else
{
stack[top]=num;
top++;
System.out.println(num+" is pushed in the stack!");
}
}

public void Pop()
{
if(top==0)
System.out.println("STACK UNDERFLOW!!!");
else
{
stack[top]=0;
top--;
System.out.println("Element poped!!!");
}
}

public void display()
{
if(top==0)
System.out.println("STACK UNDERFLOW!!NO ELEMENTS TO SHOW!!");
else
{
for(int i=top;i>0;i--)
{
if(stack[i]!=0)
System.out.print(stack[i]+" ");
else
System.out.print("");
}
}
}

public void main(String args[]) throws IOException
{
StackImplementation obj= new StackImplementation();
System.out.println("----STACK AS AN ARRAY IMPLEMENTATION----");
max=Integer.parseInt(br.readLine());
System.out.println("MAX:"+ max);
int inpt=0,n;
do
{
System.out.println("1)Enter 1 for performing Push\n2)Enter 2 for performing Pop\n3)Enter 3 for Displaying\n"
+"4)Enter 4 for Exiting");
inpt=Integer.parseInt(br.readLine());
switch(inpt)
{
case 1:
System.out.println("Enter number to be Pushed :");
n=Integer.parseInt(br.readLine());
obj.Push(n);
break;
case 2:
obj.Pop();
break;
case 3:
obj.display();
case 4:
System.out.println("******Program Terminates******");
System.exit(0);
default:
System.out.println("Wrong Entry!!");
}
}while(inpt!=4);
}
}

Well,
this is a stack as an array program.When i call the push function for the first time, the 'max' value gets changed to zero, even though its a global variable, and i accept its value from the user. Any suggestion?

how do i make it final? i have to accept the max value in the main method, and after doing dat how shall i make it final? Btw, can u tell me why does the global variable's value change in the other method?

Capture.jpg
Sorry for not being clear.The 'global' variable i was referring to was 'max'. If you see the output snapshot, when i call the Push() method, max's value gets changed to zero, even though i accepted it's value from user(6 in this case). I wanna know why that is happening.