interface stackop
{
 void push(int item);
 int pop();
}
class FixedStack implements stackop
{
 private int stk[ ];
 private int tos;
 FixedStack(int size)
 {
 stk=new int[size];
 tos=-1;
 }
 public void push(int item)
 {
 if(tos==stk.length-1)
 {
 System.out.println("Stack Overflows");
 int t[ ]=new int[stk.length * 2];
 for(int i=0;i<stk.length;i++)
 t[i]=stk[i];
 stk=t;
 stk[++tos]=item;
 }
 else
 stk[++tos]=item;
 }
 public int pop()
 {
 if(tos<0)
 {
 System.out.println("Stack Underflows");
 return 0;
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 }
 else
 return stk[tos--];
 }
}
class DynStack implements stackop
{
 private int stk[ ];
 private int tos;
 DynStack(int size)
 {
 stk=new int[size];
 tos=-1;
 }
 public void push(int item)
 {
 if(tos==stk.length-1)
 {
 System.out.println("Stack Overflows.");
 int t[ ]=new int[stk.length * 2];
 for(int i=0;i<stk.length;i++)
 t[i]=stk[i];
 stk=t;
 stk[++tos]=item;
 }
 else
 stk[++tos]=item;
 }
 public int pop()
 {
 if(tos<0)
 {
 System.out.println("Stack Underflows.");
 return 0;
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 }
 else
 return stk[tos--];
 }
}
class StackTest
{
 public static void main(String args[ ])
 {
 FixedStack fs=new FixedStack(3);
 DynStack ds=new DynStack(5);
 stackop mystk;
 for(int i=0;i<3;i++)
 fs.push(i);
 System.out.println("Fixed length Stack Contents are.");
 for(int i=0;i<3;i++)
 System.out.println(fs.pop());
 for(int i=0;i<7;i++)
 ds.push(i);
 System.out.println("Dynamic length Stack Contents are");
 for(int i=0;i<7;i++)
 System.out.println(ds.pop());
 mystk=fs;
 for(int i=0;i<3;i++)
 mystk.push(i);
 System.out.println("Fixed length Stack Contents using interface reference");
 for(int i=0;i<3;i++)
 System.out.println(mystk.pop());
 mystk=ds;
 for(int i=0;i<7;i++)
 mystk.push(i);
 System.out.println("Dynamic length Stack Contents using interface reference");
 for(int i=0;i<7;i++)
 System.out.println(mystk.pop());
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 }
}