java面试书籍2023源码

package com.wiley.javainterviewsexposed.chapter08; import org.junit.Test; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import static junit.framework.Assert.assertEquals; import static junit.framework.Assert.assertFalse; public class LinkedHashMapExample { @Test public void showLinkedHashmapProperties() { final LinkedHashMap<Integer, String> linkedHashMap = new LinkedHashMap<>(); linkedHashMap.put(10, "ten"); linkedHashMap.put(20, "twenty"); linkedHashMap.put(30, "thirty"); linkedHashMap.put(40, "forty"); linkedHashMap.put(50, "fifty"); // works like a map assertEquals("fifty", linkedHashMap.get(50)); // Respects insertion order final Iterator<Integer> keyIterator = linkedHashMap.keySet().iterator(); assertEquals("ten", linkedHashMap.get(keyIterator.next())); assertEquals("twenty", linkedHashMap.get(keyIterator.next())); assertEquals("thirty", linkedHashMap.get(keyIterator.next())); assertEquals("forty", linkedHashMap.get(keyIterator.next())); assertEquals("fifty", linkedHashMap.get(keyIterator.next())); // The same is not true for HashMap final HashMap<Integer, String> regularHashMap = new HashMap<>(); regularHashMap.put(10, "ten"); regularHashMap.put(20, "twenty"); regularHashMap.put(30, "thirty"); regularHashMap.put(40, "forty"); regularHashMap.put(50, "fifty"); final ArrayList hashMapValues = new ArrayList<>(regularHashMap.values()); final ArrayList linkedHashMapValues = new ArrayList<>(linkedHashMap.values()); // the lists will have the same values, but in a different order assertFalse(linkedHashMapValues.equals(hashMapValues)); } }