空白最终变量

Question

null

public class foo
{
    public final int smth; //Variable might not have been initialized
    public final Integer smthElse; //Variable might not have been initialized

    public foo(JSONObject myObj)
    {
        if(myObj != null) {
            try {
                int extraParam = Integer.parseInt("ABCD"); //This is just an example for Exception to be called
                smth = extraParam;
                smthElse = extraParam;
            } catch (Exception e) {}
        } else {
            smth = 1;
            smthElse = 2;
        }
    }
}

Answer 1

当myobj为null时，将不设置最终字段。这会导致编译错误，它们必须在foo（Object myObj,int extraParam)构造函数完成后设置。

如果需要创建foo的实例，可以添加els块。

public foo(Object myObj, int extraParam) {
  if (myObj != null) {
    smth = extraParam;
    smthElse = extraParam;
  } else {
    smth = 0;
    smthElse = 0;
  }
}

或者创建工厂方法来执行检查。

private foo(int extraParam) {
  smth = extraParam;
  smthElse = extraParam;
}

public static foo from(Object myObj, int extraParam) {
  return (myObj == null) ? new foo(0) : new foo(extraParam);
}