Stack. This collection is implements LIFO: the last in is the first out. We push elements onto the top of a stack and then pop them for retrieval.
This collection is deprecated—its use is discouraged in favor of Deque. It is based on Vector, which has worse performance than newer lists.
An example. Let us begin working upon a Stack. We import java.util.Stack to make the Stack type accessible. We use diamond inference syntax to declare the stack.
Start We invoke push() on the stack. When we push "fly" to the stack, the "fly" is at the top of the stack.
Then When we push "worm" and "butterfly" to the stack, the fly is now at the bottom, and "butterfly" is at the top.
Info Pop() returns (but does not remove) the topmost element of the stack (in this case "butterfly").
import java.util.Stack;
public class Program {
public static void main(String[] args) {
Stack<String> stack = new Stack<>();
stack.push("fly");
stack.push("worm");
stack.push("butterfly");
// Peek at the top of the stack.
String peekResult = stack.peek();
System.out.println(peekResult);
// Pop the stack and display the result.
String popResult = stack.pop();
System.out.println(popResult);
// Pop again.
popResult = stack.pop();
System.out.println(popResult);
}
}butterfly
butterfly
worm
Add, loop. A Stack is based on the Vector type. We can invoke all the Vector's methods: here we call add() instead of push() to add elements.
Info We can loop over a stack with its iterator in a for-loop. In this way we display all the Stack's elements.
import java.util.Stack;
public class Program {
public static void main(String[] args) {
Stack<Integer> stack = new Stack<>();
stack.add(10);
stack.add(20);
stack.add(1, 100); // We can add at a position.// Loop over int values.
for (int value : stack) {
System.out.println(value);
}
}
}10
100
20
Avoid this collection. Stack is deprecated. It still exists in the Java libraries for compatibility. When I looked for a Stack collection, it appeared in Eclipse.
However This is not the best stack-like collection. The ArrayDeque and the Deque interface are faster and newer.
Note In my experience, when a framework redesigns collections and replaces them, the newer ones are consistently better.
Stack and queues. Implementing parsers is often done with stacks. When each element is encountered, it is pushed to the stack. In older programs, this Stack is used.
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This page was last updated on May 23, 2023 (edit).