Runnable with a parameter

Question

I have a need for a  Runnable that accepts a parameter  although I know that such runnable doesn t really exist   This may point to fundamental flaw in the design of my app and or a mental block in my tired brain  so I am hoping to find here some advice on how to accomplish something like the following  without violating fundamental OO principles     private Runnable mOneShotTask   new Runnable String str        public void run String str           someFunc str                  Any idea how to accomplish something like the above

User · Answer

You could put it in a function   String paramStr    a parameter   Runnable myRunnable   createRunnable paramStr    private Runnable createRunnable final String paramStr        Runnable aRunnable   new Runnable            public void run                someFunc paramStr                         return aRunnable        When I used this  my parameter was an integer ID  which I used to make a hashmap of ID --  myRunnables  That way  I can use the hashmap to post remove different myRunnable objects in a handler

User · Answer

I would first want to know what you are trying to accomplish here to need an argument to be passed to new Runnable   or to run    The usual way should be to have a Runnable object which passes data str  to its threads by setting member variables before starting  The run   method then uses these member variable values to do execute someFunc

User · Answer

Since Java 8  the best answer is to use Consumer lt T gt    https   docs oracle com javase 8 docs api java util function Consumer html  It s one of the functional interfaces  which means you can call it as a lambda expression   void doSomething Consumer lt String gt  something        something accept  hello             doSomething   something  - gt  System out println something

User · Answer

theView post new Runnable         String str       Override                                 public void run             par Log str                                           public Runnable init String pstr            this str pstr          return this           init str      Create init function that returns object itself and initialize parameters with it

User · Answer

You have two options    Define a named class   Pass your parameter to the constructor of the named class  Have your anonymous class close over your  parameter    Be sure to mark it as final

User · Answer

Well it s been almost 9 years since I originally posted this and to be honest  Java has made a couple improvements since then  I ll leave my original answer below  but there s no need for people to do what is in it  9 years ago  during code review I would have questioned why they did it and maybe approved it  maybe not  With modern lambdas available  it s irresponsible to have such a highly voted answer recommending an antiquated approach  that  in all fairness  was dubious to begin with     In modern Java  that code review would be immediately rejected  and this would be suggested   void foo final String str        Thread t   new Thread    - gt  someFunc str        t start        As before  details like handling that thread in a meaningful way is left as an exercise to the reader  But to put it bluntly  if you re afraid of using lambdas  you should be even more afraid of multi-threaded systems   Original answer  just because   You can declare a class right in the method  void Foo String str        class OneShotTask implements Runnable           String str          OneShotTask String s    str   s            public void run                 someFunc str                       Thread t   new Thread new OneShotTask str        t start

User · Answer

I use the following class which implements the Runnable interface   With this class you can easily create new threads with arguments  public abstract class RunnableArg implements Runnable        Object   m args       public RunnableArg                public void run Object    args            setArgs args           run               public void setArgs Object    args            m args   args             public int getArgCount             return m args    null   0   m args length             public Object   getArgs             return m args

[java] Runnable with a parameter?

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