- Each time an object is created in java, it goes into an area of memory known as The Heap. ( Heap – heap is an area of pre-reserved computer main storage ( memory ) that a program process can use to store data in some variable amount that won’t be known until the program is running.)
- All Objects – no matter when , where, or how they’re created – live on the the Heap.
- But its not just any old memory heap; the Java heap is actually called the Garbage-Collectible heap.
- When you create an Object, Java Allocates memory space on the heap according how much that particular object needs.
- An Object with say , 15 instance variables, will probably need more space than an Object with only two instance variables.
- But what happens when you need to reclaim the space ? How do you get an object out of the heap when you’re done with it ? Java manages that memory for you! when the JVM can ‘see’ that an Object can never be used again, that object become eligible for garbage Collection.
- And if you’re running low on memory, the Garbage Collector will run, throw out the unreachable objects, and free up the space, so that the space can be reused.
Category: Basic – environment Setup Windows
Setup JDK, JRE, Apache Ant at Environment Variable – run on CMD Prompt
1. Download Java SE
– download : http://www.oracle.com/technetwork/java/javase/downloads/index.html
1.1. Purpose Java SE:
– “JDK” is the Java Development Kit. I.e., the JDK is bundle of software that you can use to develop Java based software.
2. Download JRE
download :http://www.oracle.com/technetwork/java/javase/downloads/index.html
2.1. Purpose of JRE:
– JRE is an implementation of the Java Virtual Machine which actually executes Java programs.
3. Apache Ant
download :http://ant.apache.org/bindownload.cgi
3.1. Purpose of Apache Ant:
– Apache Ant is a Java library and command-line tool that help building software.
4. After Download And Install – Lets Set The Environment Variable :
4.1. Click Start > Computer – Right Click > Properties > Advanced System Setting > Click Environment Variable
4.1.1. JDK –variable Name : JAVA_HOME
– Variable value: C:\Program Files\Java\jdk1.7.0_25\bin
4.1.2. JRE –Java runtime Variable : JRE_HOME
– Variable Value: C:\workspaces\java\jre1.6.0_07\bin
4.1.3. Apache Ant Variable : ANT_HOME
– Variable Value : C:\Program Files\Java\apache-ant-1.9.2\bin
5. Create a directory on your computer where java source are store
C:\java_source
5.1. Check java Version
java -version
5.2. Check the JDK Version
javac -version
5.3. Compile the java source.
Command : Javac HelloWorld.java
5.4. Run the Class Java.
Command : Java HelloWorld
Output : Hello, World!
6. Setup JDK, JRE in the Environment variable in Windows 8.
Nothing new, just search environment variable and setting like setting in Windows XP or Windows 7