CODEWITHSUNDEEP
javaobject
ILikeTurtles
ILikeTurtles

Reputation: 1022

Is it possible to make an object available everywhere in a program in java?

If I have two objects, in and out, is it possible to make those objects static or available every where? So that no matter where I am in a program I can type

out.println("Hello!");

and it functions without having to pass in and out into different objects like so?

happyCat(BufferedReader in, PrintStream out);

Please let me know if this is possible.

BufferedReader in = new BufferedReader(new InputStreamReader(server.getInputStream()));
PrintStream out = new PrintStream(server.getOutputStream());

Upvotes: 0

Views: 1048

Answers (3)

Mike Samuel
Mike Samuel

Reputation: 120516

No. In every source file, you will either have to statically import your in and out: 

import static pkg.MyGlobals.in;
import static pkg.MyGlobals.out;

or you will have to qualify uses as in 

pkg.MyGlobals.out.method(...)

There is no way to define new packages like java.lang which are implicitly imported, and there are no classes whose static members are implicitly imported.

Only the methods defined on Object are available unqualified everywhere and that is only because they are inherited in every context that can contain code that could reference them.

Section 6.5.6.1 Simple Expression Names explains how simple names like in and out are matched to fields of objects:

If an expression name consists of a single Identifier, then there must be exactly one declaration denoting either a local variable, parameter, or field visible (§6.4.1) at the point at which the Identifier occurs. Otherwise, a compile-time error occurs.

Following links from that starting point should convince you that there are no hidden mechanisms for this.

Upvotes: 0

Zólyomi István
Zólyomi István

Reputation: 2441

You can change the default in and out streams of the Java environment by calling System.setIn() and System.setOut(), see javadoc for class System here. When any piece of code references the default streams, they will be "redirected" to your instances.

System.setOut(myOutput);
System.setIn(myInput);
...
System.out.println("hello"); // This will print to your output stream
System.in.read();             // This will read from your input stream

Upvotes: 1

Thierry
Thierry

Reputation: 5233

You can create a class Streams and use static :

class Streams {
   // I don't know where "server" come from
   public static BufferedReader in = ...
   public static PrintStream out = ...

}

an then use :

 Streams.in and Streams.out

Upvotes: 1

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