sort使用比较器的字符串列表

Question

I have -

import java.util.*;

public class TestCompare {

    List<String> list = Arrays.asList("10", "1", "20", "11", "21", "12");
    Comparator<String> cmp = new Comparator<String>() {
        public int compare(String o1, String o2) {
            return Integer.valueOf(o1).compareTo(Integer.valueOf(o2));
        }
    };
    Collections.sort(list, cmp);
}

At Collections.sort(list, cmp); there is an error - Syntax error on token "(", delete this token . What is wrong in this syntax ?

Answer 1

您需要将代码包装在方法中，而不是直接在类块中。

Answer 2

You can't have code directly in a class, it should be in a method like main :

public class TestCompare {
    public static void main() {
      List<String> list = Arrays.asList("10", "1", "20", "11", "21", "12");
      Comparator<String> cmp = new Comparator<String>() {
      public int compare(String o1, String o2) {
        return Integer.valueOf(o1).compareTo(Integer.valueOf(o2));
      }
      };
      Collections.sort(list, cmp);
    }
}

Answer 3

At class level, only declarations (and initializer) blocks are allowed. Your first two statements are declarations (they are interpreted as field declarations, even though that is probably not your intention). The third is not a declaration, so it fails.

Declarations can be: methods, fields, constructors, inner classes