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Wathek Mah
Wathek Mah

Reputation: 43

Java aims to be ‘Threaded’

i need help to under stand the threads in java.

A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently.

What do we mean when we say that Java aims to be ‘Threaded’

Upvotes: 0

Views: 201

Answers (4)

Stephen C
Stephen C

Reputation: 719229

What do we mean when we say that Java aims to be ‘Threaded’

Well, literally we don't say that, because calling a runtime environment "threaded" means something rather different; see http://en.wikipedia.org/wiki/Threaded_code. (And note that that page takes care to distinguish between "threaded" and "multi-threaded"!)

In fact, we describe Java as being a language that supports "Multi-threaded" programming. The quotation in your question is a succinct description of what that means. A more long-winded description is as follows.

A program normally executes statements in sequence. So for example:

  int i = 1;
  i = i + j;
  if (i < 10) {
      ...
  }

In the above, the statements are executed one after another in sequence.

A thing that controls the execution of statements like that is called a "thread of control" or (more commonly) a thread. You can think of it as an automaton that executes statements one after another, and that is only capable of doing one at a time. It keeps a record of the state of the local variables and the procedure calls. (It typically uses a stack and a set of private registers to do this ... but that's an implementation detail.)

In a multi-threaded program, there are potentially many of these automatons, each executing a different sequence of statements (using its own stack and registers). Each thread is potentially able to communicate with other threads (by observing shared objects, etc) and can synchronize with them in various was and for various reasons.

Depending on the hardware (and the operating system), the threads may either all run on the same processor, or they may (at different times) run on different processors. It is typically a combination of the two, and it is typically up to the operating system to decide which of the threads that can do work is allowed to run. (This is handled by the thread scheduler.)

From a Java perspective, multi-threaded programming is implemented at the low level using the Thread class, synchronized methods and blocks, and the Object level wait and notify methods. Higher level APIs provide standard building blocks for solving common problems.

Upvotes: 0

Иван Бишевац
Иван Бишевац

Reputation: 14671

"Java is threaded" means that Java could execute two or more jobs at the same time.

If you want to learn more about that look at Oracle Java concurrency tutorial: http://docs.oracle.com/javase/tutorial/essential/concurrency/

Upvotes: 0

necromancer
necromancer

Reputation: 24641

threads are a popular way to implement concurrency in languages. java has them. that's what it means.

Upvotes: 2

AlexR
AlexR

Reputation: 115378

This means that various operations can and should be executed concurrently. This can be achieve by using threads. You can either use "low level" thread API (Thread, Runnable) or higher level API (Timer, Executors).

I hope this is enough to start googling and learn. I'd recommend you to start from low level threading API to understand how to work with threads and synchronization. Then go forward and learn facilities of concurrency package introduced in java 1.5. Do not start from higher level API. You need low level to understand later what happens behind the scene when you are submitting task to executor.

Upvotes: 3

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