Java-15.7 Map (1)-using arrays to simulate the creation of Map

Java-15.7 Map (1)-using arrays to simulate the creation of Map

In this chapter, we will simulate Map using arrays and learn about the creation of Map.

1. What is Map?

Map, a ing table, also called an association array, maintains the association of "key-value.

 

2. Simulate Map using Arrays

 

package com.ray.ch15;import java.util.HashSet;import java.util.Set;public class Test
 
   {public static void main(String[] args) {AssociativeArray
  
    map = new AssociativeArray
   
    (2);map.put("one", "1");map.put("two", "2");try {map.put("three", "3");} catch (Exception e) {System.out.println("too many objects");}for (String key : map.getKeySet()) {System.out.println(map.getByKey(key));}}}class AssociativeArray
    
      {private Object[][] objects;private int index = 0;public AssociativeArray(int count) {objects = new Object[count][2];}public void put(K key, V value) {if (index >= objects.length) {throw new ArrayIndexOutOfBoundsException();}objects[index++] = new Object[] { key, value };}public Set
     
       getKeySet() {Set
      
        set = new HashSet
       
        ();for (int i = 0; i < objects.length; i++) {set.add((K) objects[i][0]);}return set;}@SuppressWarnings("unchecked")public V getByKey(K key) {V v = null;for (int i = 0; i < objects.length; i++) {if (objects[i][0] == key) {v = (V) objects[i][1];}}return v;}}
       
      
     
    
   
  
 

Output:

 

Too upload objects
2
1

 

The above Code uses arrays to simulate the creation of Map.

Explanation:

(1) The above uses an Object array as the underlying data storage structure

(2) get method through array assignment

(3) Implement the getKeyset and get methods by traversing the Array

Note:

The above code is the simplest implementation, without any optimization, and there are various problems. We will end the implementation of java in the future.

Summary: This chapter describes how to use arrays to simulate the creation of map.

This chapter is here. Thank you.