Mark A. Ziesemer: Java: Iterating over XML DOM Nodes

Mark A. Ziesemer: Java: Iterating over XML DOM Nodes

(Android) How to write your code with a good style

I saw an excellent article in Android Code Source site, it is a Code Style Guide, which is Google Android team asks their developer to respect. Writing code with a good style helps others to read your code, and developer should have a good habit of writing code too.

Code Style Guide

(Java) How to stop a thread without Thread.stop()

The stop() method is deprecated, for example:

private Thread blinker;

public void start() {
blinker = new Thread(this);
blinker.start();
}

public void stop() {
blinker.stop(); // UNSAFE!
}

public void run() {
Thread thisThread = Thread.currentThread();
while (true) {
try {
thisThread.sleep(interval);
} catch (InterruptedException e){
}
repaint();
}
}

Why is Thread.stop deprecated?

Because it is inherently unsafe. Stopping a thread causes it to unlock all the monitors that it has locked. (The monitors are unlocked as the ThreadDeath exception propagates up the stack.) If any of the objects previously protected by these monitors were in an inconsistent state, other threads may now view these objects in an inconsistent state. Such objects are said to be damaged. When threads operate on damaged objects, arbitrary behavior can result. This behavior may be subtle and difficult to detect, or it may be pronounced. Unlike other unchecked exceptions, ThreadDeath kills threads silently; thus, the user has no warning that his program may be corrupted. The corruption can manifest itself at any time after the actual damage occurs, even hours or days in the future. (From java.sun.com)

To replace this method, here is an example:

private volatile Thread blinker;

public void stop() {
blinker = null;
}

public void run() {
Thread thisThread = Thread.currentThread();
while (blinker == thisThread) {
try {
thisThread.sleep(interval);
} catch (InterruptedException e){
}
repaint();
}
}

(Java) How to detect the end of a child thread

In a main thread, we could create the child thread to do some work in the same time. But how can we get the return value of a child thread before continue the main thread, we should wait the child thread finish before call the other method.

The solution is join() of Thread, it waits for this thread to die.

ChildThread ct = new ChildThread();
ct.start();
ct.join();