一類中靜態初始值設定項的初始化順序

Question

我有一個應該爲程序提供路徑的類。爲了做到這一點，它決定了Windows下的本地和漫遊數據路徑，並在Linux下取得了一個家目錄。除此之外，它提供了來自其他路徑的路徑。

它是安全的寫

public class DataDirectory { 
    public static final File ROAMING; 
    public static final File LOCAL; 

    static { 
     // set ROAMING and LOCAL 
    } 

    public static final File PROFILE = doMkdirs(new File(ROAMING, "profiles"); 
    public static final File SETUP = doMkdirs(new File(ROAMING, "setup"); 
    public static final File LOGFILES = doMkdirs(new File(ROAMING, "logfiles"); 

    private static File doMkdirs(File file) { 
     file.mkdirs(); 
     return file; 
    } 
} 

或做我必須做的

public class DataDirectory { 
    public static final File ROAMING; 
    public static final File LOCAL; 

    public static final File PROFILE; 
    public static final File SETUP; 
    public static final File LOGFILES; 

    static { 
     // set ROAMING and LOCAL 

     PROFILE = mkdirsRoaming("profiles"); 
     SETUP = mkdirsRoaming("setup"); 
     LOGFILES = mkdirsRoaming("logfiles"); 
    } 

    public static final File PROFILE = doMkdirs(new File(ROAMING, "profiles"); 
    public static final File SETUP = doMkdirs(new File(ROAMING, "setup"); 
    public static final File LOGFILES = doMkdirs(new File(ROAMING, "logfiles"); 

    private static File doMkdirs(File file) { 
     file.mkdirs(); 
     return file; 
    } 
} 

上爲了安全嗎？

Answer 1

我自己在QA風格中回答這個問題。

java規格說明the initializers are executed in textual order, as though they were a single block。

這意味着第一個版本是安全的; static { }塊之後的初始化器可以使用該塊內設置的最終變量。