限制只调用一次 static setter 方法

Question

I have the below code:

public final class SomeStaticClass {


private static  Map<String, Map<String,String>> tMap;


private SomeStaticClass(){
    //Private Constructor to avoid instance creation
}


//getter method here to retrieve the map.


public static void setMap(Map<String, Map<String,String>> map){
    
    tMap = map;
}
}

I want to restrict the setMap method to be called only once,so that the tMap cannot be modified later. The tMap will be set only once during application startup and will be access by multiple objects later.

Answer 1

public static void setMap(Map<String, Map<String,String>> map){
    
if (null == tMap) // This will make sure tMap initialized only once
    tMap = map;
}