* 运行内存-Xms512m -Xmx512m -XX:+PrintGCDetails* 测试的结果与实际两者的区别不符，ArrayList居然任何地方表现优秀* ！！！待追究原因...* * ------------------------------------------------* ArrayList  末尾添加数据[50w次]测试：执行耗时：8ms* LinkedList 末尾添加数据[50w次]测试：执行耗时：15ms* Q:* ArrayList如果没有指定大小会动态扩展，涉及到数组的复制* ------------------------------------------------* * ------------------------------------------------* ArrayList  随机位置添加数据[1w次]测试：执行耗时：516ms* LinkedList 随机位置添加数据[1w次]测试：执行耗时：3104ms* Q:* ArrayList每次随机插入时候进行一次数组的复制* 表现应该没有LinkedList优秀* ------------------------------------------------* *  ------------------------------------------------* ArrayList  随机位置删除次数[1w次]测试：执行耗时：508ms* LinkedList 随机位置删除次数[1w次]测试：执行耗时：3621ms* Q：* ArrayList 每次删除一个元素时候将进行数组的复制，引用下标-1*  因此越靠前开销越大* LinkedList删除时候判断位置是{前半段、中间、后半段}去删除* ArrayList应该没有LinkedList优秀*  ------------------------------------------------* *  ------------------------------------------------* ArrayList  forEach2循环读取测试：执行耗时：10ms* LinkedList forEach2循环读取测试：执行耗时：23ms* * ArrayList  iterator2循环读取测试：执行耗时：9ms* LinkedList iterator2循环读取测试：执行耗时：29ms* * ArrayList  for循环读取测试：执行耗时：6ms* LinkedList for循环读取测试： 无穷大...* Q:*  随机访问ArrayList优秀*  ------------------------------------------------

package com.java.essence_36;import java.util.*;/*** Created by lw on 14-5-20.* <p/>* 有序的HashMap -LinkedHashMap*/
public class Linked_HashMap {private static Map<Integer, String> integerStringMap;/*** accessOrder=true  按照元素最后访问时间排序* accessOrder=false 按照元素添加顺序排序* public LinkedHashMap(int initialCapacity,float loadFactor,boolean accessOrder) {* ..* }*/private static void InitLinked_HashMap(boolean accessOrder) {integerStringMap = new LinkedHashMap(16, 0.75f, accessOrder);integerStringMap.put(1, "a");integerStringMap.put(2, "b");integerStringMap.put(3, "c");integerStringMap.put(4, "d");System.out.println("访问key=2、3的元素....");integerStringMap.get(2);integerStringMap.get(3);System.out.println(integerStringMap);}/*** accessOrder=true  按照元素最后访问时间排序* 遍历时候由Key获取Value时候抛出java.util.ConcurrentModificationException* <p/>* 遍历时候，LinkedHashMap调用get方法会修改LinkedHashMap结构。* remove亦是。* 参考下面is2ConcurrentModificationException()方法内容*/private static void for_Linked_HashMap() {integerStringMap = new LinkedHashMap(16, 0.75f, true);integerStringMap.put(1, "a");integerStringMap.put(2, "b");integerStringMap.put(3, "c");integerStringMap.put(4, "d");Set<Integer> set = integerStringMap.keySet();for (Integer integer : set) {integerStringMap.get(integer);// integerStringMap.remove(integer);}}public static void main(String[] args) {InitLinked_HashMap(true);InitLinked_HashMap(false);//for_Linked_HashMap();is2ConcurrentModificationException();}/*** 衍生：List怎么移除元素？*      forEach怎么执行的呢？* 什么时候产生快速失败？什么时候产生安全失败？*/private static void is2ConcurrentModificationException() {String str;List<String> list = new ArrayList<String>();list.add("a");list.add("b");for (String s : list) {//list.remove(s);}Iterator<String> iterator = list.iterator();while (iterator.hasNext()) {str = iterator.next();//list.remove(str);}Map map = new HashMap();map.put(1, "a");map.put(2, "b");for (int i = 0; i < map.size(); i++) {//  map.remove(1);}Set<Integer> set = map.keySet();for (Integer integer : set) {//set.remove(integer);//yes//map.remove(integer);//yes}}
}

package com.java.essence_36;import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;/*** Created by lw on 14-5-20.* 学生姓名与成绩*/
class Student implements Comparable<Student> {String name;int score;/*** 衍生疑问：* 为什么要有构造器？* 他做了什么？* 对象到底是谁创建的？构造器里面吗？* this到底什么？*/public Student(String name, int score) {this.name = name;this.score = score;}/*** 重写排序实现方法* 按成绩比较** @param o* @return*/@Overridepublic int compareTo(Student o) {if (o.score > this.score) {return -1;}if (o.score < this.score) {return 1;}return 0;}@Overridepublic String toString() {return "Student{" +"name='" + name + '\'' +", score=" + score +'}';}
}//学生的详细信息
class Student_Message {String address;Student_Message(String address) {this.address = address;}@Overridepublic String toString() {return "address='" + address;}
}public class Tree_Map {//①：比较的对象实现了Comparable接口private static Map<Student, Student_Message> map = new TreeMap();//①：将Comparator 传入构造器private static Map<Student, Student_Message> map_1 = new TreeMap(new Comparator() {@Overridepublic int compare(Object o1, Object o2) {return 0;}@Overridepublic boolean equals(Object obj) {return false;}});/*** 衍生疑问：* 以上2种方法有什么区别。* 为什么Comparator还需要重写equals方法？*//*** 初始化treeMap*/private static void InitTreeMap() {Student yiwa = new Student("yiwa", 20);Student erwa = new Student("erwa", 30);Student sanwa = new Student("sanwa", 40);Student siwa = new Student("siwa", 80);Student wuwa = new Student("wuwa", 100);map.put(yiwa, new Student_Message("TY"));map.put(erwa, new Student_Message("TY"));map.put(sanwa, new Student_Message("TY"));map.put(siwa, new Student_Message("TY"));map.put(wuwa, new Student_Message("TY"));//查询一娃~~四娃成绩之间的学生System.out.println(((TreeMap) map).subMap(yiwa, siwa));System.out.println();//查询成绩大于一娃的学生System.out.println(((TreeMap) map).tailMap(yiwa));System.out.println();//查询成绩小于三娃的学生System.out.println(((TreeMap) map).headMap(sanwa));}public static void main(String[] args) {InitTreeMap();}
}