1 public class TestCollections { 2 public static void main(String[] args) { 3 ArrayList<String> al=new ArrayList<String>(); 4 //向集合中一次性添加N多个元素 5 Collections.addAll(al, "hello","world","java"); 6 System.out.println(al);//[hello, world, java] 7 8 //排序 9 Collections.sort(al);//为什么按照英文字母的升序排序?因为String类具备了比较大小的能力 10 System.out.println(al); //[hello, java, world] 11 12 //二分搜索 13 System.out.println(Collections.binarySearch(al, "java"));//1 14 System.out.println(Collections.binarySearch(al, "html"));//-2 -2= -(插入点+1) 推理出来插入点 1 15 16 //集合拷贝 17 ArrayList<String> al2=new ArrayList<String>(); 18 Collections.addAll(al2, "sql","sql","sql","sql4"); 19 //集合拷贝注意的地方:如果源集合.size()>目标集合的.size() IndexOutOfBoundsException 20 Collections.copy(al2, al); //将al中所有元素拷贝到al2中,[hello, java, world, sql4] 21 System.out.println(al2); 22 23 //填 充 24 Collections.fill(al2, "html");//[html, html, html, html] 25 System.out.println(al2); 26 27 //最大与最小 28 System.out.println("最大:"+Collections.max(al));//最大:world 29 System.out.println("最小:"+Collections.min(al));//最小:hello 30 31 //逆序 32 Collections.reverse(al); 33 System.out.println(al);//[world, java, hello] 34 35 //线程同步 36 List<String> list=Collections.synchronizedList(al); 37 } 38 }