不多说，直接上干货！

 

 

代码需求

 　　想从

[abcde, cba, aa, zzz, cba, nbaa]

 

　　变成

[aa, cba, cba, zzz, nbaa, abcde]

 

 

 

 

 

 

 

 

 

 

CollectionsDemo.java

package zhouls.bigdata.DataFeatureSelection.test;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

import java.util.TreeSet;

import zhouls.bigdata.DataFeatureSelection.test.ComparatorByLength;

public class CollectionsDemo {

/**

* @param args

*/

public static void main(String[] args) {

/*

* Collections：是集合框架的工具类。

* 里面的方法都是静态的。

*/

demo();

}

public static void demo(){

List list = new ArrayList();

list.add("abcde");

list.add("cba");

list.add("aa");

list.add("zzz");

list.add("cba");

list.add("nbaa");

System.out.println(list);

//对list集合进行指定顺序的排序。

Collections.sort(list);

mySort(list);

mySort(list,new ComparatorByLength());

Collections.sort(list,new ComparatorByLength());

System.out.println(list);

}

public static void mySort(List list,Comparator comp){

for (int i = 0; i < list.size()-1; i++) {

for (int j = i+1; j < list.size(); j++) {

if(comp.compare(list.get(i), list.get(j))>0){

T temp = list.get(i);

list.set(i, list.get(j));

list.set(j, temp);

Collections.swap(list, i, j);

}

}

}

}

public static > void mySort(List list){

for (int i = 0; i < list.size()-1; i++) {

for (int j = i+1; j < list.size(); j++) {

if(list.get(i).compareTo(list.get(j))>0){

// T temp = list.get(i);

// list.set(i, list.get(j));

// list.set(j, temp);

Collections.swap(list, i, j);

}

}

}

}

}

 

 

 

 

 

ComparatorByLength.java

package zhouls.bigdata.DataFeatureSelection.test;

import java.util.Comparator;

public class ComparatorByLength implements Comparator {

public int compare(String o1, String o2) {

int temp = o1.length() - o2.length();

return temp==0?o1.compareTo(o2): temp;

}

}

 

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