Collection tool class

package com.zhang.collection_;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.Iterator;public class Collections_ {public static void main(String[] args) {ArrayList list = new ArrayList();list.add("jack");list.add("blank");list.add("ann");list.add("lucy");list.add("KK");System.out.println("Original collection"+list);//swap(List, int, int) swaps the two int position elements in the listCollections.swap(list,0,3);System.out.println("After swap"+list);//sort(list) Sorts the specified List in ascending order according to the natural order of the elements (by string size)Collections.sort(list);System.out.println("After natural sorting"+list);//sort(list.Comparator): Sort the List collection according to the specified Comparator generation orderCollections.sort(list, new Comparator() {@Overridepublic int compare(Object o1, Object o2) {return ((String)o1).length() - ((String)o2).length();}});System.out.println("After sorting by length" + list);//reverse() reverse the elementCollections.reverse(list);System.out.println("After reversing the order"+list);//shuffle() shuffles the elementsCollections.shuffle(list);System.out.println("After scrambled"+list);//Object max(Collections) Returns the largest element in the collection according to the natural ordering of the elements.System.out.println("Maximum element in natural order" + Collections.max(list));//Object max(Collections Comparator): According to the order of Comparator, return the largest element in the collectionSystem.out.println("Return the element with the largest length"+Collections.max(list, new Comparator() {@Overridepublic int compare(Object o1, Object o2) {return ((String)o1).length() - ((String)o2).length();}}));//Object min(Collections) According to the natural sorting of elements, return the smallest element in the collection//Object max(Collections Comparator): According to the order of Comparator, return the smallest element in the collection//Same as above o1 o2 position swap//int frequency(Collections,Object) Returns the number of occurrences of the specified elementSystem.out.println("Number of occurrences of KK"+ Collections.frequency(list,"KK"));//void copy(List dest, list list) copies the contents of the list to dest//If the original set src size is larger than the subsequent dest, an exception will be thrownArrayList dest = new ArrayList();//In order to complete the copy, we must first assign a value to dest, the size is the same as the size of srcfor (int i = 0; i 原网站
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