集合框架-工具类-Collections-逆序替换

package cn.itcast.p2.toolclass.collections.demo;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;

import cn.itcast.p2.comparator.ComparatorByLength;

public class CollectionsDemo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        /*
         * Collections：是集合框架的工具类。
         * 里面的方法都是静态的。
         */
//        demo_1();//排序
//        demo_2();//折半 最值
//        demo_3();//逆序 
        demo_4();//替换

    }
    
    

    private static void demo_4() {
        // TODO Auto-generated method stub
        List<String> list = new ArrayList<String>();
        
        list.add("abcde");
        list.add("cba");
        list.add("zhangsan");
        list.add("zhaoliu");
        list.add("xiaoqiang");
        
        System.out.println(list);
//        Collections.replaceAll(list, "cba", "nba");//replaceAll相当于set(indexOf"cba","nba");
//        Collections.fill(list, "cc");//fill一次性将集合的所有值替换或重新初始化一次
        Collections.shuffle(list);//随机将元素安在任意位置
        System.out.println(list);
    }

    private static void demo_3() {
        // TODO Auto-generated method stub
        
//        TreeSet<String> ts = new TreeSet<String>(Collections.reverseOrder());//原理就是下面这个方法
    /*    TreeSet<String> ts = new TreeSet<String>(new Comparator<String>() {
            public int compare(String o1, String o2) {
                int temp = o2.compareTo(o1);
                return temp;
            }
        });
        */ //自己实现
        
        //reverseOrder(Comparator<T> cmp),将一个已有比较器逆转
        TreeSet<String> ts = new TreeSet<String>(Collections.reverseOrder(new ComparatorByLength()));
        ts.add("abc");
        ts.add("hahaha");
        ts.add("zzz");
        ts.add("aa");
        ts.add("cba");
        
        System.out.println(ts);
    }

    private static void demo_2() {
        // TODO Auto-generated method stub
        List<String> list = new ArrayList<String>();
        
        list.add("abcde");
        list.add("cba");
        list.add("aa");
        list.add("zzz");
        list.add("cba");
        list.add("nbaa");
        //折半要先排序
        Collections.sort(list);
        System.out.println(list);
        
        int index = Collections.binarySearch(list, "aaa");
        
        System.out.println("index="+index);
        
        //获取最大值。
//        String max = Collections.max(list);//max=zzz
        String max = Collections.max(list,new ComparatorByLength());
        System.out.println("max="+max);
    }

    public static void demo_1() {
        
        List<String> list = new ArrayList<String>();
        
        list.add("abcde");
        list.add("cba");
        list.add("aa");
        list.add("zzz");
        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());
        System.out.println(list);
        
        
    }
    //下面方法相当于Collections.sort(list,new ComparatorByLength);
    /*
    public static <T> void mySort(List<T> list,Comparator<? super T> 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);
                    }
                }
            }
        }
    //介绍Collections.swap交换方法
    /*
    public static <T extends Comparable<? super T>> void mySort(List<T> 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);
                }
            }
        }
    }*/
    
    //相当于按自然顺序方法升序排列Collections.sort
    //public static <T extends Comparable<? super T>> void sort(List<T> list)
    /*
    public static <T extends Comparable<? super T>> void mySort(List<T> 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);
                }
            }
        }
    }*/
    
    //传入String类型的集合
 /*    public static void mySort(List<String> 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 ) {
                    String temp = list.get(i);
                    list.set(i, list.get(j));
                    list.set(j, temp);
                }
            }
        }
    }*/

}