java - java中使用随机数的列表

Question

我有以下代码

public class ShufflingListAndArray
{
  public static void main(String[] args) throws IOException

{
    List services = new ArrayList (


    Arrays.asList("COMPUTER", "DATA", "PRINTER"));

   Random rnd=new Random();
  String s = services.get(rnd.nextInt(services.size()));

    Collections.shuffle(list);


    //Collections.sort(list);


    System.out.println("List sorting :"+ list);
  }
} 

编译上述程序时出现以下错误。

C:\>javac ShufflingListAndArray.java
ShufflingListAndArray.java:12: asList(java.lang.Object[]
nnot be applied to (java.lang.String,java.lang.String,ja
    Arrays.asList("COMPUTER", "DATA", "PRINTER"));


          ^
ShufflingListAndArray.java:15: cannot resolve symbol
symbol  : variable rnd
location: class ShufflingListAndArray
  String s = services.get(rnd.nextInt(services.size()));
                          ^
ShufflingListAndArray.java:15: incompatible types
found   : java.lang.Object
required: java.lang.String
  String s = services.get(rnd.nextInt(services.size()));
                         ^
ShufflingListAndArray.java:17: cannot resolve symbol
symbol  : variable list
location: class ShufflingListAndArray
    Collections.shuffle(list);
                        ^
ShufflingListAndArray.java:19: cannot resolve symbol
symbol  : variable list
location: class ShufflingListAndArray
    System.out.println("List sorting :"+ list);
                                         ^
5 errors

请帮我解决错误。非常感谢......

Answer 1

...
Arrays.asList("COMPUTER", "DATA", "PRINTER"));

从编译器错误中可以看出，它接受一个数组作为输入，而不是一系列字符串。您可以通过:

...
Arrays.asList(new String[] {"COMPUTER", "DATA", "PRINTER"}));

其次，您的“服务”引用不使用泛型类型，因此其内容具有编译时类型“对象”而不是“字符串”。相反，你想要:

List<String> services = new ArrayList<String>(

第三，变量的名称是“services”而不是“list”，因此:

Collections.shuffle(services);

最后的声明也是如此。在这种情况下，编译器几乎可以准确地告诉您问题是什么。你读过它的输出吗？