Here are my development principals in java world.
When you installed many of jdk versions, there are two ways to switch the jdk.
After a lot of googing a found simple way solution, I’d like to share.
Edit your profile /.bash_profile or /.zshrc
alias java_ls='/usr/libexec/java_home -V 2>&1 | grep -E "\d.\d.\d[,_]" | cut -d , -f 1 | colrm 1 4 | grep -v Home'
function java_use() {
export JAVA_HOME=$(/usr/libexec/java_home -v $1)
export PATH=$JAVA_HOME/bin:$PATH
java -version
}
Execute java_ls
1.8.0_11
1.7.0_45
1.6.0_65-b14-462
1.6.0_65-b14-462
Execute java_use 1.8
java version "1.8.0_11"
Java(TM) SE Runtime Environment (build 1.8.0_11-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.11-b03, mixed mode)A Reader/Writer are designed for character-oriented streams. If the information we are reading is all text, then the Reader will take care of character decoding for you. For example, you can read all in text file to represent the characters in Java.
An InputStream/OutStream are designed for byte-oriented streams. It grabs/writes the data byte by byte without performing any kind of translation. For example, you can read/write image data, mp3…or any binary files.
The observer pattern is a behavioral design pattern which defines a one-to-many relationship between objects. When the observable object changes its state, all dependent objects are notified and updated automatically. In stock market case, a stock trading system keeps track of all trades of specific stocks (subjects) and must inform all trader (observers) when a new trade has been made for new prices.
Observer
someone who sees or notices something
Observable
something that is observable can be seen or measured
To be honest, I don’t want the Observable class to be tightly coupled with the classes that are interested in observing it. It doesn’t care who it is as long as it fulfils certain criteria. I think we might consider the event-bus if there are a lot of usage in your system. There are two reasons :
The Java wait-and-notify mechanism is a way for inter thread communcation in Java. It allows one thread to communicate to another thread that a particular condition has occured. The wait-and-notify mechanism cannot be used to replace the synchronized mechanism and does not solve the race condition problem. In fact, wait-and-notify must be used in conjunction with the synchronized lock to prevent a race condition.
Just like the synchronized mechanism, the wait-and-notify mechanism is available from every object. There are three methods to invoke on any object should have the object monitor.
wait()
The current thread must own this object’s monitor. The thread releases ownership of this monitor and waits until another thread notifies threads waiting on this object’s monitor to wake up either through a call to the notify method or the notifyAll method.
notify()
Wakes up a single thread that is waiting on this object’s monitor. If any threads are waiting on this object, one of them is chosen to be awakened. The choice is arbitrary and occurs at the discretion of the implementation. A thread waits on an object’s monitor by calling one of the wait methods.
notifyAll()
Wakes up all threads that are waiting on this object’s monitor.
On the other question, wait and notify method are used to put thread on wait but they are not in Thread class along with Sleep() or Join() method instead they are declared in Object class. This article has few reasons which make sense on Why Wait and Notify is in Object Class in Java.
If you want to search the new job and don’t want your employer to know that you’re updating your profile, I suggested to turn off your activity broadcasts. It’s a good idea to avoid annoying messages. Here’s how to turn off your activity broadcasts.
The comparable and Comparator are two interfaces provided by Java Core API. They used to compare stuff in some way for sorting and ordering objects in Java. But what they exactly are and what is different between them? In this tutorial we will see their usage.
Comparable interface has only one method called compareTo and its purpose is to define the natural ordering of an object. Specifically, compareTo() method should need to return an integer as follows:
For example consider the real case where we have a Name class:
Comparator interface gives you the capability to sort a given collection any number of different ways to pas to methods such as Collections.sort() or Arrays.sort(). So you might want to create a Comparator object for the following ideas.
Sometimes, to write the comparaTo() or compare() methods are very bored and the code will also not be readable. Guava ComparisonChain allows you to check whether an object is less-than or greater-than another object by comparing multiple properties. It should be used the both of Comparable and Comparator.