BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
UNIT II
INTRODUCTION TO JAVA
HISTORY OF JAVA
The history of Java is very interesting. Java was originally designed for interactive television, but it
was too advanced technology for the digital cable television industry at the time. The history of Java
starts with the Green Team. Java team members (also known as Green Team), initiated this project
to develop a language for digital devices such as set-top boxes, televisions, etc. However, it was suited
for internet programming. Later, Java technology was incorporated by Netscape.
The principles for creating Java programming were "Simple, Robust, Portable, Platform-independent,
Secured, High Performance, Multithreaded, Architecture Neutral, Object-Oriented, Interpreted, and
Dynamic". Java was developed by James Gosling, who is known as the father of Java, in 1995. James
Gosling and his team members started the project in the early '90s.
Currently, Java is used in internet programming, mobile devices, games, e-business solutions, etc.
There are given significant points that describe the history of Java.
1) James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June
1991. The small team of sun engineers called Green Team.
2) Initially designed for small, embedded systems in electronic appliances like set-top boxes.
3) Firstly, it was called "Greentalk" by James Gosling, and the file extension was .gt.
4) After that, it was called Oak and was developed as a part of the Green project.
Why Java named "Oak"?
5) Why Oak? Oak is a symbol of strength and chosen as a national tree of many countries like the
U.S.A., France, Germany, Romania, etc.
6) In 1995, Oak was renamed as "Java" because it was already a trademark by Oak Technologies.
Why Java Programming named "Java"?
7) Why had they chosen java name for Java language? The team gathered to choose a new name.
The suggested words were "dynamic", "revolutionary", "Silk", "jolt", "DNA", etc. They wanted
something that reflected the essence of the technology: revolutionary, dynamic, lively, cool, unique,
and easy to spell and fun to say.
According to James Gosling, "Java was one of the top choices along with Silk". Since Java was so
unique, most of the team members preferred Java than other names.
1
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
8) Java is an island of Indonesia where the first coffee was produced (called java coffee). It is a kind
of espresso bean. Java name was chosen by James Gosling while having coffee near his office.
9) Notice that Java is just a name, not an acronym.
10) Initially developed by James Gosling at Sun Microsystems (which is now a subsidiary of Oracle
Corporation) and released in 1995.
11) In 1995, Time magazine called Java one of the Ten Best Products of 1995.
12) JDK 1.0 released in(January 23, 1996). After the first release of Java, there have been many
additional features added to the language. Now Java is being used in Windows applications, Web
applications, enterprise applications, mobile applications, cards, etc. Each new version adds the new
features in Java.
JAVA VERSION HISTORY
Many java versions have been released till now. The current stable release of Java is Java SE 10.
1. JDK Alpha and Beta (1995)
2. JDK 1.0 (23rd Jan 1996)
3. JDK 1.1 (19th Feb 1997)
4. J2SE 1.2 (8th Dec 1998)
5. J2SE 1.3 (8th May 2000)
6. J2SE 1.4 (6th Feb 2002)
7. J2SE 5.0 (30th Sep 2004)
8. Java SE 6 (11th Dec 2006)
9. Java SE 7 (28th July 2011)
10. Java SE 8 (18th Mar 2014)
11. Java SE 9 (21st Sep 2017)
12. Java SE 10 (20th Mar 2018)
13. Java SE 14.0. 2 (March 2020)
THE JAVA VIRTUAL MACHINE
What is JVM?
Java Virtual Machine (JVM) is a engine that provides runtime environment to drive the Java Code
or applications. It converts Java bytecode into machines language. JVM is a part of Java Run
Environment (JRE). In other programming languages, the compiler produces machine code for a
particular system. However, Java compiler produces code for a Virtual Machine known as Java Virtual
Machine.
2
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
Here is how JVM works
First, Java code is complied into bytecode. This bytecode gets interpreted on different machines
Between host system and Java source, Bytecode is an intermediary language. JVM is responsible for
allocating memory space.
JVM Architecture
Let's understand the Architecture of JVM. It contains classloader, memory area, execution engine etc.
1) ClassLoader
The class loader is a subsystem used for loading class files. It performs three major functions viz.
Loading, Linking, and Initialization.
2) Method Area
JVM Method Area stores class structures like metadata, the constant runtime pool, and the code for
methods.
3) Heap
All the Objects, their related instance variables, and arrays are stored in the heap. This memory is
common and shared across multiple threads.
4) JVM language Stacks
Java language Stacks store local variables, and it’s partial results. Each thread has its own JVM stack,
created simultaneously as the thread is created. A new frame is created whenever a method is invoked,
3
and it is deleted when method invocation process is complete.
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
5) PC Registers
PC register store the address of the Java virtual machine instruction which is currently executing. In
Java, each thread has its separate PC register.
6) Native Method Stacks
Native method stacks hold the instruction of native code depends on the native library. It is written in
another language instead of Java.
7) Execution Engine
It is a type of software used to test hardware, software, or complete systems. The test execution engine
never carries any information about the tested product.
8) Native Method interface
The Native Method Interface is a programming framework. It allows Java code which is running in a
JVM to call by libraries and native applications.
9) Native Method Libraries
Native Libraries is a collection of the Native Libraries(C, C++) which are needed by the Execution
Engine.
Why is Java both Interpreted and Compiled Language?
Programming languages are classified as
Higher Level Language Ex. C++, Java
Middle-Level Languages Ex. C
Low-Level Language Ex Assembly
finally the lowest level as the Machine Language.
A compiler is a program which converts a program from one level of language to another. Example
conversion of C++ program into machine code.
The java compiler converts high-level java code into bytecode (which is also a type of machine code).
An interpreter is a program which converts a program at one level to another programming language
at the same level. Example conversion of Java program into C++
In Java, the Just In Time Code generator converts the bytecode into the native machine code which
are at the same programming levels.
Hence, Java is both compiled as well as interpreted language.
4 Page
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
UNIT II
INTRODUCTION TO JAVA
HISTORY OF JAVA
The history of Java is very interesting. Java was originally designed for interactive television, but it
was too advanced technology for the digital cable television industry at the time. The history of Java
starts with the Green Team. Java team members (also known as Green Team), initiated this project
to develop a language for digital devices such as set-top boxes, televisions, etc. However, it was suited
for internet programming. Later, Java technology was incorporated by Netscape.
The principles for creating Java programming were "Simple, Robust, Portable, Platform-independent,
Secured, High Performance, Multithreaded, Architecture Neutral, Object-Oriented, Interpreted, and
Dynamic". Java was developed by James Gosling, who is known as the father of Java, in 1995. James
Gosling and his team members started the project in the early '90s.
Currently, Java is used in internet programming, mobile devices, games, e-business solutions, etc.
There are given significant points that describe the history of Java.
1) James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June
1991. The small team of sun engineers called Green Team.
2) Initially designed for small, embedded systems in electronic appliances like set-top boxes.
3) Firstly, it was called "Greentalk" by James Gosling, and the file extension was .gt.
4) After that, it was called Oak and was developed as a part of the Green project.
Why Java named "Oak"?
5) Why Oak? Oak is a symbol of strength and chosen as a national tree of many countries like the
U.S.A., France, Germany, Romania, etc.
6) In 1995, Oak was renamed as "Java" because it was already a trademark by Oak Technologies.
Why Java Programming named "Java"?
7) Why had they chosen java name for Java language? The team gathered to choose a new name.
The suggested words were "dynamic", "revolutionary", "Silk", "jolt", "DNA", etc. They wanted
something that reflected the essence of the technology: revolutionary, dynamic, lively, cool, unique,
and easy to spell and fun to say.
According to James Gosling, "Java was one of the top choices along with Silk". Since Java was so
unique, most of the team members preferred Java than other names.
1
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
8) Java is an island of Indonesia where the first coffee was produced (called java coffee). It is a kind
of espresso bean. Java name was chosen by James Gosling while having coffee near his office.
9) Notice that Java is just a name, not an acronym.
10) Initially developed by James Gosling at Sun Microsystems (which is now a subsidiary of Oracle
Corporation) and released in 1995.
11) In 1995, Time magazine called Java one of the Ten Best Products of 1995.
12) JDK 1.0 released in(January 23, 1996). After the first release of Java, there have been many
additional features added to the language. Now Java is being used in Windows applications, Web
applications, enterprise applications, mobile applications, cards, etc. Each new version adds the new
features in Java.
JAVA VERSION HISTORY
Many java versions have been released till now. The current stable release of Java is Java SE 10.
1. JDK Alpha and Beta (1995)
2. JDK 1.0 (23rd Jan 1996)
3. JDK 1.1 (19th Feb 1997)
4. J2SE 1.2 (8th Dec 1998)
5. J2SE 1.3 (8th May 2000)
6. J2SE 1.4 (6th Feb 2002)
7. J2SE 5.0 (30th Sep 2004)
8. Java SE 6 (11th Dec 2006)
9. Java SE 7 (28th July 2011)
10. Java SE 8 (18th Mar 2014)
11. Java SE 9 (21st Sep 2017)
12. Java SE 10 (20th Mar 2018)
13. Java SE 14.0. 2 (March 2020)
THE JAVA VIRTUAL MACHINE
What is JVM?
Java Virtual Machine (JVM) is a engine that provides runtime environment to drive the Java Code
or applications. It converts Java bytecode into machines language. JVM is a part of Java Run
Environment (JRE). In other programming languages, the compiler produces machine code for a
particular system. However, Java compiler produces code for a Virtual Machine known as Java Virtual
Machine.
2
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
Here is how JVM works
First, Java code is complied into bytecode. This bytecode gets interpreted on different machines
Between host system and Java source, Bytecode is an intermediary language. JVM is responsible for
allocating memory space.
JVM Architecture
Let's understand the Architecture of JVM. It contains classloader, memory area, execution engine etc.
1) ClassLoader
The class loader is a subsystem used for loading class files. It performs three major functions viz.
Loading, Linking, and Initialization.
2) Method Area
JVM Method Area stores class structures like metadata, the constant runtime pool, and the code for
methods.
3) Heap
All the Objects, their related instance variables, and arrays are stored in the heap. This memory is
common and shared across multiple threads.
4) JVM language Stacks
Java language Stacks store local variables, and it’s partial results. Each thread has its own JVM stack,
created simultaneously as the thread is created. A new frame is created whenever a method is invoked,
3
and it is deleted when method invocation process is complete.
Page
, BCA - JAVA
YUVAKSHETRA INSTITUTE OF MANAGEMENT STUDIES BCA 2017 ONWARS BATCH
PRORAMMING
5) PC Registers
PC register store the address of the Java virtual machine instruction which is currently executing. In
Java, each thread has its separate PC register.
6) Native Method Stacks
Native method stacks hold the instruction of native code depends on the native library. It is written in
another language instead of Java.
7) Execution Engine
It is a type of software used to test hardware, software, or complete systems. The test execution engine
never carries any information about the tested product.
8) Native Method interface
The Native Method Interface is a programming framework. It allows Java code which is running in a
JVM to call by libraries and native applications.
9) Native Method Libraries
Native Libraries is a collection of the Native Libraries(C, C++) which are needed by the Execution
Engine.
Why is Java both Interpreted and Compiled Language?
Programming languages are classified as
Higher Level Language Ex. C++, Java
Middle-Level Languages Ex. C
Low-Level Language Ex Assembly
finally the lowest level as the Machine Language.
A compiler is a program which converts a program from one level of language to another. Example
conversion of C++ program into machine code.
The java compiler converts high-level java code into bytecode (which is also a type of machine code).
An interpreter is a program which converts a program at one level to another programming language
at the same level. Example conversion of Java program into C++
In Java, the Just In Time Code generator converts the bytecode into the native machine code which
are at the same programming levels.
Hence, Java is both compiled as well as interpreted language.
4 Page
