Stack (linear structure)

1. A stack is a First in, then out (FILO-First In Last Out) Ordered list of .
2. Stack (stack) Is to limit the insertion and deletion of elements in a linear table Only on the same end of the linear table A special linear table for carrying out . The side that allows insertion and deletion , For the end of change , be called To the top of the stack (Top), The other end is the fixed end , be called At the bottom of the stack (Bottom).
3. According to the definition of stack , First put the elements in the stack at the bottom of the stack , The last element put in is at the top of the stack , Deleting elements is the opposite , The last element is deleted first , The first element to be placed is deleted .

The illustration

Code

Notes have ideas to explain ~

package com.atguigu.stack;

import java.util.Scanner;

//author qij
public class ArrayStackDemo {
    

	public static void main(String[] args) {
    
		// Test it ArrayStack  Whether it is right 
		// So let's create one ArrayStack object -> Presentation stack 
		ArrayStack stack = new ArrayStack(4);
		String key = "";
		boolean loop = true; // Controls whether to exit the menu 
		Scanner scanner = new Scanner(System.in);
		
		while(loop) {
    
			System.out.println("show:  Indicates the display stack ");
			System.out.println("exit:  Exit procedure ");
			System.out.println("push:  Indicates adding data to the stack ( Push )");
			System.out.println("pop:  Indicates fetching data from the stack ( Out of the stack )");
			System.out.println(" Please enter your choice ");
			key = scanner.next();
			switch (key) {
    
			case "show":
				stack.list();
				break;
			case "push":
				System.out.println(" Please enter a number ");
				int value = scanner.nextInt();
				stack.push(value);
				break;
			case "pop":
				try {
    
					int res = stack.pop();
					System.out.printf(" The data out of the stack is  %d\n", res);
				} catch (Exception e) {
    
					// TODO: handle exception
					System.out.println(e.getMessage());
				}
				break;
			case "exit":
				scanner.close();
				loop = false;
				break;
			default:
				break;
			}
		}
		
		System.out.println(" Program exit ~~~");
	}

}

// Define a  ArrayStack  Presentation stack 
class ArrayStack {
    
	private int maxSize; //  The size of the stack 
	private int[] stack; //  Array , Array simulation stack , The data is in this array 
	private int top = -1;// top Represents the top of the stack , Initialize to -1
	
	// Constructors 
	public ArrayStack(int maxSize) {
    
		this.maxSize = maxSize;
		stack = new int[this.maxSize];
	}
	
	// Stack full 
	public boolean isFull() {
    
		return top == maxSize - 1;
	}
	// The stack is empty 
	public boolean isEmpty() {
    
		return top == -1;
	}
	// Push -push
	public void push(int value) {
    
		// First, judge whether the stack is full 
		if(isFull()) {
    
			System.out.println(" Stack full ");
			return;
		}
		top++;
		stack[top] = value;
	}
	// Out of the stack -pop,  Return the data at the top of the stack to 
	public int pop() {
    
		// First, judge whether the stack is empty 
		if(isEmpty()) {
    
			// Throw an exception 
			throw new RuntimeException(" The stack is empty , No data ~");
		}
		int value = stack[top];
		top--;
		return value;
	}
	// Show the stack [ Traversal stack ],  Ergodic time , You need to display data from the top of the stack 
	public void list() {
    
		if(isEmpty()) {
    
			System.out.println(" The stack is empty , No data ~~");
			return;
		}
		// You need to display data from the top of the stack 
		for(int i = top; i >= 0 ; i--) {
    
			System.out.printf("stack[%d]=%d\n", i, stack[i]);
		}
	}
	
}