Java 对无序集合的元素进行排序

java中的无序集合不提供任何顺序，也就是说，不能像List这样的有序集合那样使用特定的索引或顺序来访问这些元素。集合和Map是无序集合的例子。

在java中，我们不能直接使用Collections.shuffle()方法对无序集合进行洗牌，因为它需要一个List作为参数。

用于洗牌的元素。

我们必须首先将无序集合的元素存储在一个List中，然后我们可以使用Collections.shuffle()方法对其进行洗牌。

1) 洗涤一个集合的元素

// Java program to demonstrate the shuffling
// of a set
 
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // Creating a Hashset
        Set<Integer> st = new HashSet<>();
 
        // Inserting elements to the set
        st.add(91);
        st.add(0);
        st.add(55);
        st.add(10);
        st.add(9);
 
        // 9 won't be inserted to the Set as Hashset does
        // not take duplicate entries
        st.add(9);
 
        // Displaying the elements of the set
        System.out.print("The Set before shuffling: ");
       
        for (int i : st)
            System.out.print(i + " ");
       
        System.out.println();
 
        // Creating a List and storing the values of the
        // Set inside it by passing the Set as a parameter
        // to the constructor
        List<Integer> list = new ArrayList<>(st);
 
        // Shuffling the elements of the list using
        // Collections.shuffle() method
        Collections.shuffle(list);
 
        // Displaying the elements of the list
        System.out.print("The List (containing elements of the Set) after shuffling: ");
       
        for (int i : list)
            System.out.print(i + " ");
    }
}

输出

The Set before shuffling: 0 55 9 10 91 
The List (containing elements of the Set) after shuffling: 55 0 91 10 9

2) 洗涤Map上的元素

// Java program to demonstrate the shuffling
// of a map
 
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // Creating a HashMap
        Map<Integer, String> mp
            = new HashMap<Integer, String>();
 
        // Inserting some values inside the HashMap
        mp.put(1, "Geeks");
        mp.put(2, "for");
        mp.put(3, "Geeks");
        mp.put(4, "is");
        mp.put(5, "love");
 
        // Displaying the map
        System.out.println("The Map before shuffling: ");
       
        for (Map.Entry<Integer, String> entry :mp.entrySet())
            System.out.println(entry.getKey() + " "
                               + entry.getValue());
       
        System.out.println();
 
        // Creating a list and storing the elements of the
        // Map inside of it
        List<Map.Entry<Integer, String> > list
            = new ArrayList<>(mp.entrySet());
 
        // Shuffling the list using shuffle() method
        Collections.shuffle(list);
 
        // Displaying the list
        System.out.println("The List (containing the elements of the Map)"
                           + " After shuffing: ");
       
        for (Map.Entry<Integer, String> entry : list)
            System.out.println(entry.getKey() + " "
                               + entry.getValue());
        System.out.println();
    }
}

输出

The Map before shuffling: 
1 Geeks
2 for
3 Geeks
4 is
5 love

The List (containing the elements of the Map) After shuffing: 
2 for
5 love
4 is
3 Geeks
1 Geeks