集合(Collections-sort)-(Collections-max)-(Collections-binarySearch)

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集合框架的工具类
Collections;
import java.util.*;class CollectionsDemo{    public static void main(String[] args)    {        binarySearchDemo();    }         public static void binarySearchDemo()    {        List<String> list = new ArrayList<String>();                 list.add("abcd");        list.add("aaa");        list.add("zz");        list.add("kkkkk");        list.add("qq");        list.add("z");                 Collections.sort(list);                 sop(list);        // int index = Collections.binarySearch(list,"aaaa");        int index = halfSearch(list,"aaaa");        sop("index="+index);    }         public static int halfSearch(List<String> list,String key,Comparator<String> cmp)    {        int max,min,mid;        max = list.size()-1;        min = 0;                 while(min<=max)        {            mid = (max+min)>>1;// /2;                         String str = list.get(mid);                         // int num = str.compareTo(key);            int num = cmp.compare(str,key);            if(num>0)                max = mid - 1;            else if(num<0)                min = mid + 1;            else                return mid;        }        return -min-1;    }         public static void maxDemo()    {        List<String> list = new ArrayList<String>();                 list.add("abcd");        list.add("aaa");        list.add("zz");        list.add("kkkkk");        list.add("qq");        list.add("z");        Collections.sort(list);        sop(list);        String max = Collections.max(list);        sop("max="+max);    }         public static void sortDemo()    {        List<String> list = new ArrayList<String>();                 list.add("abcd");        list.add("aaa");        list.add("zz");        list.add("kkkkk");        list.add("qq");        list.add("z");                      sop(list);                 // Collections.sort(list);        Collections.sort(list,new StrLenComparator());        sop(list);    }         public static void sop(Object obj)    {        System.out.println(obj);    }} class StrLenCompatator implements Comparator<String>{    public int compare(String s1,String s2)    {        if(s1.length()>s2.length())            return 1;        if(s1.length()<s2.length())            return -1;        return s1.compareTo(s2);    }}
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