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Stack in Java Programming
Stack is a subclass of Vector that implements a standard last-in, first-out stack.
Stack only defines the default constructor, which creates an empty stack. Stack includes all the methods defined by Vector, and adds several of its own.
Stack( )
Apart from the methods inherited from its parent class Vector, Stack defines the following methods −
| Sr.No. | Method & Description |
|---|---|
| 1 | boolean empty() Tests if this stack is empty. Returns true if the stack is empty, and returns false if the stack contains elements. |
| 2 | Object peek( ) Returns the element on the top of the stack, but does not remove it. |
| 3 | Object pop( ) Returns the element on the top of the stack, removing it in the process. |
| 4 | Object push(Object element) Pushes the element onto the stack. Element is also returned. |
| 5 | int search(Object element) Searches for element in the stack. If found, its offset from the top of the stack is returned. Otherwise, -1 is returned. |
Example
The following program illustrates several of the methods supported by this collection.
import java.util.*;
public class StackDemo {
static void showpush(Stack st, int a) {
st.push(new Integer(a));
System.out.println("push(" + a + ")");
System.out.println("stack: " + st);
}
static void showpop(Stack 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 st = new Stack();
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");
}
}
}
Output
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 stack
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