java基础入门----Collections1 集合框架工具类

import java.util.*;class Collections1  //集合框架工具类 {public static void sop(Object obj){System.out.println(obj);}public static void main(String[] args){//sortDemo();   //排序方法//maxDemo();//取最大就是去排序完后最后的元素//binarySearchDemo(); //折半查找/*List<String> list = new ArrayList<String>();list.add("asdf");list.add("ed");list.add("vfvf");list.add("addee");Collections.sort(list);sop(list);sop(halfSearchDemo(list,"ed"));Collections.sort(list,new StrLennComparator());sop(list);sop(halfSearchDemo2(list,"ed",new StrLennComparator()));*/}public static void sortDemo(){List<String> list = new ArrayList<String>();list.add("asdf");list.add("ed");list.add("vfvf");list.add("addee");Collections.sort(list);sop(list);Collections.sort(list,new StrLennComparator());sop(list);}public static void maxDemo(){List<String> list = new ArrayList<String>();list.add("asdf");list.add("ed");list.add("vfvf");list.add("addee");Collections.sort(list);sop(list);sop(Collections.max(list));Collections.sort(list,new StrLennComparator());sop(list);sop(Collections.max(list,new StrLennComparator()));}public static void binarySearchDemo(){List<String> list = new ArrayList<String>();list.add("asdf");list.add("ed");list.add("vfvf");list.add("addee");Collections.sort(list);//Collections.sort(list,new StrLennComparator());sop(list);int index = Collections.binarySearch(list, "vfvf"/*,new StrLennComparator()*/);sop("index="+index);}public static int halfSearchDemo(List<String> list, String key)//二半查找原理{int max,min,mid;max = list.size()-1;min = 0;while(min <= max){mid = (max+min)/2;String str = list.get(mid);int num = str.compareTo(key);if(num>0)max = mid-1;else if(num<0)min = mid+1;elsereturn mid;}return -min-1;}public static int halfSearchDemo2(List<String> list, String key,Comparator<String> cmp){int max,min,mid;max = list.size()-1;min = 0;while(min <= max){mid = (max+min)/2;String str = list.get(mid);int num = cmp.compare(str, key);if(num>0)max = mid-1;else if(num<0)min = mid+1;elsereturn mid;}return -min-1;}}class StrLennComparator 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);}}