将线程级局部变量从一个 class 传递到另一个

Question

Below is the scenario.

public class A{
   private final B b;

   public A(){
     this.b = new B();
     this.c = new C();
   }

   public void setValue(){
      this.b.value("HELLO WORLD")
      this.c.print();
   }
}

Setting "Hello World" to text

public class B{
    public volatile String text;
    public B(){
        this.text = "";
    }
    public void value(String t){
        this.text = t;
    }
}

unable to get "Hello World". its coming back as ""

public class C{
    private final B b;
    public B(){
        this.b = new B;
    }
    public void print(){
        System.out.println(this.b.text);
    }
}

Any Help will be appreciated. I need a solution to pass value to one class to another

Answer 1

I think the assignment inside the constructor of B is causing you the problem. As you have made text volatile so every time you create an instance of B, the value of text is overwritten by "" and then all thread will read this updated value. Just make text variable static and then you can get the "Hello World" in class C.

Answer 2

I got the answer, have to send the reference of B to C from A

public class A{
   private final B b;
   private final C c;

   public A(){
     this.b = new B();
     this.c = new C (this.b);
   }

   public void setValue(){
      this.b.value("HELLO WORLD");
      this.c.print();
   }
}


public class B{
    public volatile String text;
    public B(){
        this.text = "";
    }
    public void value(String t){
        this.text = t;
    }
}


public class C{
    private final B b;
    public C(B b){
        this.b = b;
    }
    public void print(){
        System.out.println(this.b.text);
    }
}