Java Stack Class
Stack is a subclass of Vector, which implements a standard last-in, first-out stack.
Stack only defines the default constructor, which is used to create an empty stack. In addition to all methods defined by Vector, Stack also defines some of its own methods.
Stack()
In addition to all methods defined by Vector, it also defines some of its own methods:
| No. | Method Description |
|---|---|
| 1 |
boolean empty() Tests whether the stack is empty. |
| 2 |
Object peek( ) Looks at the object at the top of the stack without removing it from the stack. |
| 3 |
Object pop( ) Removes the object at the top of the stack and returns that object as the value of this function. |
| 4 |
Object push(Object element) Pushes an item onto the top of the stack. |
| 5 |
int search(Object element) Returns the 1-based position of the object in the stack. |
Example
The following program illustrates several methods supported by this collection.
Example
import java.util.*;
public class StackDemo {
static void showpush(Stack<Integer> st, int a) {
st.push(new Integer(a));
System.out.println("push(" + a + ")");
System.out.println("stack: " + st);
}
static void showpop(Stack<Integer> st) {
System.out.print("pop -> ");
Integer a = (Integer) st.pop();
System.out.println(a);
System.out.println("stack: " + st);
}
public static void main(String args[]) {
Stack<Integer> st = new Stack<Integer>();
System.out.println("stack: " + st);
showpush(st, 42);
showpush(st, 66);
showpush(st, 99);
showpop(st);
showpop(st);
showpop(st);
try {
showpop(st);
} catch (EmptyStackException e) {
System.out.println("empty stack");
}
}
}
The result of compiling and running the above example is as follows:
stack: [ ] push(42) stack: [42] push(66) stack: [42, 66] push(99) stack: [42, 66, 99] pop -> 99 stack: [42, 66] pop -> 66 stack: [42] pop -> 42 stack: [ ] pop -> empty stackOther Extensions