Java的数据结构

谈Java数据结构之前先聊聊C的数据结构

常见的数据结构有线性表、链表、队列、堆栈、树、图等

像压缩可以选择用树

像数据库索引可以选择用B+树

Java代码实例

Stack的代码

package com.fuping.liuqu.demo.test; import java.util.Stack; public class DataStructureDemo { public static void main(String[] args) { Stack<String> stack = new Stack<>(); stack.add("first"); String pop = stack.pop(); System.out.println(pop); System.out.println(stack.size()); stack.add("two"); String peek = stack.peek(); System.out.println(peek); System.out.println(stack.size()); stack.push("23"); stack.push("24"); stack.push("25"); stack.addElement("26"); stack.insertElementAt("34", 5); peek = stack.peek(); System.out.println(peek); System.out.println(stack.size()); pop = stack.pop(); System.out.println(pop); System.out.println(stack.size()); } }

代码运行的结果 

two 1 two 2 push:23 26 7 26 6 Process finished with exit code 0

 线性表

package com.fuping.liuqu.demo.test; import java.util.ArrayList; import java.util.List; public class DataStructureDemo { public static void main(String[] args) { List<String> list = new ArrayList<>(16); list.add("first"); System.out.println(list); } }

链表 

package com.fuping.liuqu.demo.test; import java.util.LinkedList; public class DataStructureDemo { public static void main(String[] args) { LinkedList<String> linkedList = new LinkedList<>(); linkedList.add("twe"); linkedList.add("first"); System.out.println(linkedList); } }

 结果

[twe, first] Process finished with exit code 0

队列 

package com.fuping.liuqu.demo.test; import java.util.Queue; import java.util.concurrent.ConcurrentLinkedQueue; public class DataStructureDemo { public static void main(String[] args) { Queue<String> queue = new ConcurrentLinkedQueue<>(); queue.add("first"); queue.add("two"); String element = queue.element(); System.out.println(element); } }

 结果

first Process finished with exit code 0 package com.fuping.liuqu.demo.test; import java.util.NavigableMap; import java.util.TreeMap; public class DataStructureDemo { public static void main(String[] args) { // 导航函数Map NavigableMap<String, String> navigableMap = new TreeMap<>(); // key是弱键 WeakHashMap<String, String> weakHashMap = new WeakHashMap<>(); } }

 

BlockingQueue、BlockingDeque LinkedBlockingQueue        无界队列，注意OOM，注意最大线程数的陷阱， Executors.newFixedThreadPool()的底层队列，Executors.newSingleThreadExecutor()的底层队列 ArrayBlockingQueue          有界队列，注意OOM DelayQueue                 延迟队列，Redis底层实现的队列 DelayedWorkQueue          JDK内部实现队列，Executors.newScheduledThreadPool()底层实现队列 PriorityQueue            优先级队列，可自定义排序，默认自然排序 PriorityBlockingQueue       优先级阻塞队列 ConcurrentSkipListMap      跳跃表Map，查询快 ConcurrentSkipListSet    跳跃表Set ConcurrentLinkedMap        同步的链表Map CopyOnWriteArrayList        写入时复制数组List，类似于Linux底层的Copy-On-Write技术，例如配置、黑名单、物流地址等变化非常少的数据，这是一种无锁的实现。可以帮我们实现程序更高的并发。可参考学习：https://baijiahao.baidu.com/s?id=1636057331750965212&wfr=spider&for=pc CopyOnWriteArraySet        写入时复制数组Set TransferQueue               抢占式队列，分公平式与非公平式，默认非公平 SychronousQueue          同步队列，Executors.newCachedThreadPool()的底层实现队列 TreeMap                     有序Map TreeSet                    有序Set