编程挑战：Java设计模式中的单例模式实现及测试

原创小灰灰 2024-11-22 22:33 17阅读 0赞

**单例模式实现**

在Java中，单例模式通常通过以下方式实现：

1. 静态内部类（Singleton Class as Static Inner Class）
```java
public class Singleton {
    private static Singleton instance = new Singleton();

// Getter and Setter methods if needed

public static Singleton getInstance() {
        return instance;
    }

// Private constructor to avoid instantiation from outside
    private Singleton() {}
}
```
2.枚举（Singleton via Enum）
```java
public enum Singleton {
    INSTANCE;

public void doSomething() {
        // Your method implementation here
    }
}
```
3.懒汉式单例（Singleton with Lazy Initialization）
```java
public class Singleton {
    private static Singleton instance = new Singleton();

public static Singleton getInstance() {
        return instance;
    }

// Prevent instantiation from outside
    private Singleton() {}
}
```
**测试**

对于以上的实现，我们可以编写单元测试来确保单例模式的正确性。

例如，对于懒汉式单例，测试`getInstance()`方法是否正确返回唯一实例：
```java
import org.junit.Before;
import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class SingletonTest {

private Singleton instance;

@Before
    public void setup() {
        // Initialize instance if not done in setup method
        this.instance = Singleton.getInstance();
    }

@Test
    public void testGetInstance() {
        assertEquals(instance, Singleton.getInstance());  // Test that same instance is returned every time
    }
}
```
确保在每次测试运行时，`Singleton.getInstance()`始终返回相同的实例。