Java实现的数组去重与排序操作详解

// 声明int 数组，并初始化int[] intArry = {5,4,7,8,2,0,1,9,3,6,10};// 对int数组进行排序Arrays.sort(intArry);

package com.gjnote.test.array;import java.util.Arrays;import org.junit.Test;public class TestArraysSort {// 声明int 数组，并初始化int[] intArry = {5,4,7,8,2,0,1,9,3,6,10};@Testpublic void test() {// 对int数组进行排序Arrays.sort(intArry);for (int i = 0; i < intArry.length; i++) {System.out.println(intArry[i]);}System.out.println(Arrays.toString(intArry));}}

/*** 使用 Collections.sort(list, Comparator(){});* 对List数组排序 推荐使用方法*/public void collectionsSortElement1(List list) {Collections.sort(list, new Comparator() {@Overridepublic int compare(String o1, String o2) {// 根据实际排序需要调整compareTo对象顺序return (o2).compareTo(o1);}});}

List tempList = new ArrayList();// 去除原始List中的重复元素for (String string : originalList) {if (!tempList.contains(string)) {tempList.add(string);}}

// Set 利用Set元素唯一性，去重Set set = new HashSet(originalList);List tempList = new ArrayList(set);

TreeSet treeSet = new TreeSet(originalList);ListtempList = new ArrayList();tempList.addAll(treeSet);// treeSet 默认的排序为升序，根据实际情况添加是否需要反排序Collections.reverse(tempList);

package com.gjnote.test.array;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.HashSet;import java.util.List;import java.util.Set;import java.util.TreeSet;import org.junit.Before;import org.junit.Test;/*** Test Class*List 数组去重 元素排序** @version 1.0* @author www.gjnote.com**/public class TestListArraySort {private ListoriginalList = null;@Beforepublic void setUp() throws Exception {originalList = new ArrayList();for (int i = 10000; i > 0; i--) {originalList.add("element" + i);// add repeat elementif(i % 2 == 0) {originalList.add("element" + i);}}}/*** 输出List 元素* @param list*/private void outputList(List list) {for (int i = 0; i < list.size(); i++) {System.out.println(list.get(i));}}/*** 使用 Collections.sort(list, Comparator(){});* 排序 推荐方法*/private void collectionsSortElement(List list) {long start = System.currentTimeMillis();Collections.sort(list, new Comparator() {@Overridepublic int compare(String o1, String o2) {// 根据实际排序需要调整compareTo对象顺序return o2.compareTo(o1);}});//outputList(tempList);System.out.println("Collections.sort："+ (System.currentTimeMillis() - start) + "ms");}/*** 测试 使用for循环遍历去除重复元素* Collections.sort排序*/@Testpublic void testForLoopRemoveRepeatElement() {System.out.println("testForLoopRemoveRepeatElement");long start = System.currentTimeMillis();List tempList = new ArrayList();// 去除重复元素for (String string : originalList) {if (!tempList.contains(string)) {tempList.add(string);}}// 排序collectionsSortElement(tempList);//outputList(tempList);System.out.println("使用for循环遍历List，去除重复元素: "+ (System.currentTimeMillis() - start) + "ms");}/*** 测试 使用Set去重；* 使用Collections.sort(list, Comparator(){});排序**/@Testpublic void testSetRemoveRepeatElement() {System.out.println("testSetRemoveRepeatElement");long start = System.currentTimeMillis();// 先排序 (理论值：先排序后去重会比后排序效率更高)collectionsSortElement(originalList);// Set 利用Set元素唯一性，去重Set set = new HashSet(originalList);List tempList = new ArrayList(set);// 后排序 可以注释先排序，开启后排序试试运行时间//collectionsSortElement(tempList);//outputList(tempList);System.out.println("Collections.sort排序，使用Set去重："+ (System.currentTimeMillis() - start) + "ms");}/*** 测试 使用 TreeSet去除重复元素* 默认排序或Collections.reverse翻转排序*/@Testpublic void testTreeSetRemoveRepeatElement() {System.out.println("testTreeSetRemoveRepeatElement");long start = System.currentTimeMillis();TreeSettreeSet = new TreeSet(originalList);ListtempList = new ArrayList();tempList.addAll(treeSet);// treeSet 默认的排序为升序，根据实际情况添加是否需要反排序Collections.reverse(tempList);//outputList(tempList);System.out.println("使用 TreeSet排序，去除重复元素："+ (System.currentTimeMillis() - start) + "ms");}@Testpublic void testMethods() {//outputList(originalList);// List 去重 推荐方法testSetRemoveRepeatElement();// 14mstestTreeSetRemoveRepeatElement();// 20ms//testForLoopRemoveRepeatElement();// 2525ms}}