如何在android中實現單例模式

Question

我必須在android中使用單例模式。爲了獲得更好的性能，最好使用單例類。在我的應用程序中，API調用更多，所以我決定製作一個通用解析類，用於解析值。我想把它作爲單例，所以每個活動都使用這個類，最後創建這個類的單個實例。請對此提出建議。

public class parsingclass { 
    Context context; 

    public parsingclass(Context context) { 
     this.context = context; 
    } 

    public void parsing methods() 
    { 
     //methods for parsing values 
    } 
} 

//更新的代碼

public class Singleton { 
    private static Singleton instance = null; 

    //a private constructor so no instances can be made outside this class 
    private Singleton() {} 

    //Everytime you need an instance, call this 
    public static Singleton getInstance() { 
     if(instance == null) 
      instance = new Singleton(); 

     return instance; 
    } 
    public List<String> parsing_home() 
    { 
     List<String> set=new ArrayList<String>(); 
     return set; 

    } 

    public List<String> parsing_home1() 
    { 
     List<String> set=new ArrayList<String>(); 
     return set; 

    } 

    //Initialize this or any other variables in probably the Application class 
    public void init(Context context) {} 
} 

//調用的功能

List<String> check=Singleton.getInstance().parsing_home(); 
    List<String> check1=Singleton.getInstance().parsing_home1(); 

Answer 1

使用此，

public class Singleton { 

    private static Singleton instance = null; 

    //a private constructor so no instances can be made outside this class 
    private Singleton() {} 

    //Everytime you need an instance, call this 
    //synchronized to make the call thread-safe 
    public static synchronized Singleton getInstance() { 
     if(instance == null) 
      instance = new Singleton(); 

     return instance; 
    } 

    //Initialize this or any other variables in probably the Application class 
    public void init(Context context) {} 

} 

編輯

的呼籲，getInstance線程安全的加入​​通過@SwederSchellens的建議。