JAVA - 創造主要方法數組列表和其他類中使用它無需重新創建它

Question

所以這是我的數組中的主要方法：

ArrayList<String> myarray = new ArrayList<>(); 
while(scan.hasNextLine()){ 
    myarray.add(scan.nextLine()); 
} 
scan.close(); 

我的應用程序有多個線程，我試圖用這個數組（每個線程都有一個巨大的數組），而不是每次重新創建數組。 主要思想是以某種方式加載並準備好由其他類調用。

Answer 1

可能低於給你一些想法

class Myclass{ 
    private ArrayList<String> myarray = new ArrayList<>(); 
    main(){ 
     //populate the array 
    } 
    public ArrayList<String> getList(){ 
     return myarray; 
    } 

} 

Answer 2

繼SHG建議：

public MyStaticClass { 
    // from your question is not clear whether you need a static or non static List 
    // I will assume a static variable is ok 
    // the right-hand member should be enough to synchornize your ArrayList 
    public static List<String> myarray = Collections.synchronizedList(new ArrayList<String>()); 

    public static void main(String[] args) { 
     // your stuff (which contains scanner initialization?) 

     ArrayList<String> myarray = new ArrayList<>(); 
     while(scan.hasNextLine()){ 
      myarray.add(scan.nextLine()); 
     } 
     scan.close(); 

     // your stuff (which contains thread initialization?) 
    } 

但如果你真的需要一個非靜態變量

public MyClass { 

    private final List<String> myarray; 

    public MyClass() { 
     // the right-hand member should be enough to synchornize your ArrayList 
     myarray = Collections.synchronizedList(new ArrayList<String>()); 
    } 

    public void getArray() { 
     return myarray; 
    } 


    public static void main(String[] args) { 
     // your stuff (which contains scanner initialization?) 

     Myclass myObj = new MyClass(); 
     List<String> myObjArray = myObj.getArray(); 
     while(scan.hasNextLine()){ 
      myObjArray.add(scan.nextLine()); 
     } 
     scan.close(); 

     // your stuff (which contains thread initialization?) 
    } 

有關細節靜態與非靜態字段看看Oracle documentation（基本上，你會或不會需要一個MyClass實例獲得myarray訪問權限，但是您將或不會在JVM中擁有不同的列表）。