冒泡排序

public class BubbleSort {
    public static void bubbleSort(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n-1; i++) {
            for (int j = 0; j < n-i-1; j++) {
                if (arr[j] > arr[j+1]) {
                    // 交换arr[j]和arr[j+1]
                    int temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
                }
            }
        }
    }

    public static void main(String[] args) {
        int[] arr = {64, 34, 25, 12, 22, 11, 90};
        bubbleSort(arr);
        System.out.println("排序后的数组：");
        for (int i : arr) {
            System.out.print(i + " ");
        }
    }
}

单例模式

在Java中，可以使用以下几种方式实现单例模式：

1. 懒汉式（Lazy Initialization）：

   public class Singleton {
    private static Singleton instance;
    
    private Singleton() {}
    
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
   }

2. 饿汉式（Eager Initialization）：

   public class Singleton {
    private static final Singleton instance = new Singleton();
    
    private Singleton() {}
    
    public static Singleton getInstance() {
        return instance;
    }
   }

3. 双重检查锁定（Double-Checked Locking）：

   public class Singleton {
    private volatile static Singleton instance;
    
    private Singleton() {}
    
    public static Singleton getInstance() {
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }
   }

4. 静态内部类（Static Inner Class）：

   public class Singleton {
    private static class SingletonHolder {
        private static final Singleton INSTANCE = new Singleton();
    }
    
    private Singleton() {}
    
    public static Singleton getInstance() {
        return SingletonHolder.INSTANCE;
    }
   }

这些是常见的几种实现单例模式的方式，具体选择哪种方式取决于项目需求和线程安全性要求。