//注意：Collection值接口，Collections是类
class CollectionDemo1{
public static void fun1(){
List<String> str=new ArrayList<>();
str.add("zhangsan");
str.add("wangwu");
str.add("liliu");
System.out.println("交换顺序之前:");
for (String string : str) {
System.out.println(string+" ");
}
System.out.println();
Collections.swap(str, 1, 2);
System.out.println("交换顺序之后：");
for (String string : str) {
System.out.println(string+" ");
}
System.out.println();
Collections.sort(str);
System.out.println("按照自然顺序排列：");//会按照字符串的顺序排列
for (String string : str) {
System.out.println(string+" ");
}
System.out.println("二分法查找：");
int s = Collections.binarySearch(str, "wangwu");
System.out.println(s);
System.out.println("打乱顺序");
Collections.shuffle(str);
for (String string : str) {
System.out.println(string+" ");
}
System.out.println("填充：");
Collections.fill(str, "Jolin");
for (String string : str) {
System.out.println(string+" "); //内容全部会变成Jolin
}
}
}