【Java】Collections.shuffle 洗牌方法，随机重排序一组元素

▚ 01 Collections.shuffle介绍

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📢 Java Collections shuffle() 是一个Java Collections 类方法，通过随机化排列指定的列表元素来工作。根据其参数的不同，可以划分为两种不同类型的Java shuffle()：

• 1. Java Collections shuffle(list)方法
• 2. Java Collections shuffle(list, random)方法

1.1 shuffle(list)

• shuffle(list)方法使用默认的随机性对指定的列表元素进行随机重新排序。

1.2 shuffle(list, random)

• shuffle(list, random)方法使用指定的随机性对指定的列表元素进行随机重新排序。

1.3 句法

• shuffle()方法的声明如下：

public static void shuffle(List<?> list)  
public static void shuffle(List<?> list, Random random)  
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1.4 参数

1.5 返回值

• shuffle() 方法：不返回任何值。

1.6 异常

• UnsupportedOperationException 如果指定的列表或其列表迭代器不支持set操作，此方法将引发异常。

1.7 版本的兼容性

• Java 1.5 及以上版本。

▚ 02 示例演示

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2.1 示例1 (shuffle_list_integer)

• 🍁源代码为：

import java.util.*;

public class shuffle_list_integer {
    public static void main(String[] args) {
        List<Integer> list = Arrays.asList(1,2,3,4,5,6);
        
        System.out.println("Before shuffle: " + list);
        Collections.shuffle(list);
        System.out.println("After shuffle (default): " + list);
        
        list = Arrays.asList(1,2,3,4,5,6);
        Collections.shuffle(list, new Random(10));
        System.out.println("After shuffle (new Random(10)): " + list);
        
        list = Arrays.asList(1,2,3,4,5,6);
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
        
        list = Arrays.asList(1,2,3,4,5,6);
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
    }
}
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• 🍏输出结果为：

Before shuffle: [1, 2, 3, 4, 5, 6]
After shuffle (default): [4, 5, 1, 2, 6, 3]
After shuffle (new Random(10)): [6, 3, 5, 2, 1, 4]
After shuffle (new Random(100)): [3, 6, 4, 5, 1, 2]
After shuffle (new Random(100)): [3, 6, 4, 5, 1, 2]
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2.2 示例2 (shuffle_list_string)

• 🍁源代码为：

import java.util.*;

public class shuffle_list_string {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("Apple", "Banana", "Orange", "Watermelon", "Cherry", "Peach");
        System.out.println("Before shuffle: " + list);
        
        Collections.shuffle(list);
        System.out.println("After shuffle (default): " + list);
        
        list = Arrays.asList("Apple", "Banana", "Orange", "Watermelon", "Cherry", "Peach");
        Collections.shuffle(list, new Random(10));
        System.out.println("After shuffle (new Random(10)): " + list);
        
        list = Arrays.asList("Apple", "Banana", "Orange", "Watermelon", "Cherry", "Peach");
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
        
        list = Arrays.asList("Apple", "Banana", "Orange", "Watermelon", "Cherry", "Peach");
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
    }
}
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• 🍏输出结果为：

Before shuffle: [Apple, Banana, Orange, Watermelon, Cherry, Peach]
After shuffle (default): [Banana, Watermelon, Peach, Orange, Apple, Cherry]
After shuffle (new Random(10)): [Peach, Orange, Cherry, Banana, Apple, Watermelon]
After shuffle (new Random(100)): [Orange, Peach, Watermelon, Cherry, Apple, Banana]
After shuffle (new Random(100)): [Orange, Peach, Watermelon, Cherry, Apple, Banana]
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2.3 示例3 (shuffle_linkedlist_integer)

• 🍁源代码为：

import java.util.*;

public class shuffle_linkedlist_integer {
    public static void main(String[] args) {
        LinkedList<Integer> list = new LinkedList<Integer>();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        System.out.println("Before shuffle: " + list);
        
        Collections.shuffle(list);
        System.out.println("After shuffle (default): " + list);
        
        list.clear();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        Collections.shuffle(list, new Random(10));
        System.out.println("After shuffle (new Random(10)): " + list);
        
        list.clear();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
        
        list.clear();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
    }
}
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• 🍏输出结果为：

Before shuffle: [1, 2, 3, 4, 5, 6]
After shuffle (default): [4, 1, 3, 2, 5, 6]
After shuffle (new Random(10)): [6, 3, 5, 2, 1, 4]
After shuffle (new Random(100)): [3, 6, 4, 5, 1, 2]
After shuffle (new Random(100)): [3, 6, 4, 5, 1, 2]
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2.4 示例4 (shuffle_linkedlist_string)

• 🍁源代码为：

import java.util.*;

public class shuffle_linkedlist_string {
    public static void main(String[] args) {
        LinkedList<String> list = new LinkedList<String>();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");
        list.add("Watermelon");
        list.add("Cherry");
        list.add("Peach");
        System.out.println("Before shuffle: " + list);

        Collections.shuffle(list);
        System.out.println("After shuffle (default): " + list);
       
        list.clear();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");
        list.add("Watermelon");
        list.add("Cherry");
        list.add("Peach");
        Collections.shuffle(list, new Random(10));
        System.out.println("After shuffle (new Random(10)): " + list);
        
        list.clear();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");
        list.add("Watermelon");
        list.add("Cherry");
        list.add("Peach");
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
        
        list.clear();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");
        list.add("Watermelon");
        list.add("Cherry");
        list.add("Peach");
        Collections.shuffle(list, new Random(100));
        System.out.println("After shuffle (new Random(100)): " + list);
    }
}
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• 🍏输出结果为：

Before shuffle: [Apple, Banana, Orange, Watermelon, Cherry, Peach]
After shuffle (default): [Peach, Banana, Cherry, Watermelon, Orange, Apple]
After shuffle (new Random(10)): [Peach, Orange, Cherry, Banana, Apple, Watermelon]
After shuffle (new Random(100)): [Orange, Peach, Watermelon, Cherry, Apple, Banana]
After shuffle (new Random(100)): [Orange, Peach, Watermelon, Cherry, Apple, Banana]
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参考材料

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• Java Collections.shuffle