Principles.
There were five primary goals in the creation of the Java language:
- It must be "simple, object-oriented and familiar"
- It must be "robust and secure"
- It must be "architecture-neutral and portable"
- It must execute with "high performance"
- It must be "interpreted, threaded, and dynamic"
There were five primary goals in the creation of the Java language:
- It must be "simple, object-oriented and familiar"
- It must be "robust and secure"
- It must be "architecture-neutral and portable"
- It must execute with "high performance"
- It must be "interpreted, threaded, and dynamic"
Versions.
Major release versions of Java, along with their release dates:
- JDK 1.0 (January 21, 1996)
- JDK 1.1 (February 19, 1997)
- J2SE 1.2 (December 8, 1998)
- J2SE 1.3 (May 8, 2000)
- J2SE 1.4 (February 6, 2002)
- J2SE 5.0 (September 30, 2004)
- Java SE 6 (December 11, 2006)
- Java SE 7 (July 28, 2011)
- Java SE 8 (March 18, 2014)
Major release versions of Java, along with their release dates:
- JDK 1.0 (January 21, 1996)
- JDK 1.1 (February 19, 1997)
- J2SE 1.2 (December 8, 1998)
- J2SE 1.3 (May 8, 2000)
- J2SE 1.4 (February 6, 2002)
- J2SE 5.0 (September 30, 2004)
- Java SE 6 (December 11, 2006)
- Java SE 7 (July 28, 2011)
- Java SE 8 (March 18, 2014)
Practices.
Java Platform.
One design goal of Java is portability, which means that programs written for the Java platform must run similarly on any combination of hardware and operating system with adequate run time support. This is achieved by compiling the Java language code to an intermediate representation called Java byte code, instead of directly to architecture-specific machine code. Java byte code instructions are analogous to machine code, but they are intended to be executed by a virtual machine (VM) written specifically for the host hardware.End users commonly use a Java Run time Environment (JRE) installed on their own machine for standalone Java applications, or in a web browser for Java applets.Standardized libraries provide a generic way to access host-specific features such as graphics, threading, and networking.A major benefit of using byte code is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native execute ables would. Just-in-Time (JIT) compilers were introduced from an early stage that compile byte codes to machine code during run time. Java is platform independent. But as Java virtual machine must convert Java byte code into machine language which depends on the operating system being used, it is platform dependent.
One design goal of Java is portability, which means that programs written for the Java platform must run similarly on any combination of hardware and operating system with adequate run time support. This is achieved by compiling the Java language code to an intermediate representation called Java byte code, instead of directly to architecture-specific machine code. Java byte code instructions are analogous to machine code, but they are intended to be executed by a virtual machine (VM) written specifically for the host hardware.End users commonly use a Java Run time Environment (JRE) installed on their own machine for standalone Java applications, or in a web browser for Java applets.Standardized libraries provide a generic way to access host-specific features such as graphics, threading, and networking.A major benefit of using byte code is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native execute ables would. Just-in-Time (JIT) compilers were introduced from an early stage that compile byte codes to machine code during run time. Java is platform independent. But as Java virtual machine must convert Java byte code into machine language which depends on the operating system being used, it is platform dependent.
Implementations.
Oracle Corporation is the current owner of the official implementation of the Java SE platform, following their acquisition of Sun Micro systems on January 27, 2010. This implementation is based on the original implementation of Java by Sun. The Oracle implementation is available for Microsoft Windows, Mac OS X, Linux and Solaris. Because Java lacks any formal standardization recognized by Ecma International, ISO/IEC, ANSI, or other third-party standards organization, the Oracle implementation is the de facto standard.The Oracle implementation is packaged into two different distributions: The Java Runtime Environment (JRE) which contains the parts of the Java SE platform required to run Java programs and is intended for end users, and the Java Development Kit (JDK), which is intended for software developers and includes development tools such as the Java compiler,Java doc, Jar, and a debugger Open JDK is another notable Java SE implementation that is licensed under the GNU GPL. The implementation started when Sun began releasing the Java source code under the GPL. As of Java SE 7, Open JDK is the official Java reference implementation..The goal of Java is to make all implementations of Java compatible. Historically, Sun's trademark license for usage of the Java brand insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Windows with Java.Platform-independent Java is essential to Java EE, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications.
Oracle Corporation is the current owner of the official implementation of the Java SE platform, following their acquisition of Sun Micro systems on January 27, 2010. This implementation is based on the original implementation of Java by Sun. The Oracle implementation is available for Microsoft Windows, Mac OS X, Linux and Solaris. Because Java lacks any formal standardization recognized by Ecma International, ISO/IEC, ANSI, or other third-party standards organization, the Oracle implementation is the de facto standard.The Oracle implementation is packaged into two different distributions: The Java Runtime Environment (JRE) which contains the parts of the Java SE platform required to run Java programs and is intended for end users, and the Java Development Kit (JDK), which is intended for software developers and includes development tools such as the Java compiler,Java doc, Jar, and a debugger Open JDK is another notable Java SE implementation that is licensed under the GNU GPL. The implementation started when Sun began releasing the Java source code under the GPL. As of Java SE 7, Open JDK is the official Java reference implementation..The goal of Java is to make all implementations of Java compatible. Historically, Sun's trademark license for usage of the Java brand insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Windows with Java.Platform-independent Java is essential to Java EE, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications.
Performance.
Programs written in Java have a reputation for being slower and requiring more memory than those written in C++. However, Java programs' execution speed improved significantly with the introduction of Just-in-time compilation in 1997/1998 for Java 1.1, the addition of language features supporting better code analysis (such as inner classes, the String Builder class, optional assertions, etc.), and optimizations in the Java virtual machine, such as HotSpot becoming the default for Sun's JVM in 2000.
Some platforms offer direct hardware support for Java; there are micro controllers that can run Java in hardware instead of a software Java virtual machine, and ARM based processors can have hardware support for executing Java byte code through their Jazelle option.
Programs written in Java have a reputation for being slower and requiring more memory than those written in C++. However, Java programs' execution speed improved significantly with the introduction of Just-in-time compilation in 1997/1998 for Java 1.1, the addition of language features supporting better code analysis (such as inner classes, the String Builder class, optional assertions, etc.), and optimizations in the Java virtual machine, such as HotSpot becoming the default for Sun's JVM in 2000.
Some platforms offer direct hardware support for Java; there are micro controllers that can run Java in hardware instead of a software Java virtual machine, and ARM based processors can have hardware support for executing Java byte code through their Jazelle option.
Syntax.
The traditional "Hello, world!" program can be written in Java as.
class HelloWorldApp {
public static void main(String[] args) {
System.out.println("Hello World!"); // Prints the string to the console.
}
}
The traditional "Hello, world!" program can be written in Java as.
class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); // Prints the string to the console. } }