Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
for various design choices in the language and platform. Such criticisms include the implementation of generics, the handling of unsigned numbers, the implementation of floating-point arithmetic, and security vulnerabilities. Additionally, Java, especially its early versions, has been criticized for its performance compared to other programming languages. Many have adapted Sun's phrase of "write once, run everywhere" to "write once, debug everywhere" in reference to the numerous differences in underlying platform which still must be taken into account when writing all but the most trivial of Java programs.
In a broad definition, generic programming is a style of computer programming in which algorithms are written in terms of to-be-specified-later types that are then instantiated when needed for specific types provided as parameters...
were added to Java 5.0, there was already a large framework of classes (many of which were already deprecated
Deprecation
In the process of authoring computer software, its standards or documentation, deprecation is a status applied to software features to indicate that they should be avoided, typically because they have been superseded...
), so generics were chosen to be implemented using erasure to allow for migration compatibility and re-use of these existing classes. This limited the features that could be provided by this addition as compared to other languages.
Because generics were implemented using type erasure
Type erasure
In programming languages, type erasure refers to the compile-time process by which explicit type annotations are removed from a program, before it is executed at run-time. An operational semantics that does not require programs to be accompanied by types is called a type-erasure semantics, to be...
the actual type of a template parameter is unavailable at runtime. Thus, the following operations are not possible in java:
public class MyClass {
public static void myMethod(Object item) {
if (item instanceof E) { //Compiler error
...
}
E item2 = new E; //Compiler error
E[] iArray = new E[10]; //Compiler error
}
}
In computer science, an integer is a datum of integral data type, a data type which represents some finite subset of the mathematical integers. Integral data types may be of different sizes and may or may not be allowed to contain negative values....
types. Unsigned data is often generated from programs written in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
and the lack of these types prevents direct data interchange between C and Java. Unsigned large numbers are also used in a number of numeric processing fields, including cryptography, which can make Java more inconvenient to use for these tasks.
Although it is possible to partially circumvent this problem with conversion code and using larger data types, it makes using Java cumbersome for handling unsigned data. While a 32-bit signed integer may be used to hold a 16-bit unsigned value losslessly, a 32-bit unsigned value would require a 64bit signed integer, and a 64bit unsigned value cannot be stored using any integer type in Java because no type larger than 64 bits exists in the Java language. In all cases, the memory consumed is doubled, and any logic that depends on the rules of two's complement
Two's complement
The two's complement of a binary number is defined as the value obtained by subtracting the number from a large power of two...
overflow must typically be rewritten. If abstracted using functions, function calls become necessary for many operations which are native to some other languages. Alternatively, it is possible to use Java's signed integers to emulate unsigned integers of the same size, but this requires detailed knowledge of complex bitwise operations.
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
arithmetic is largely based on IEEE 754 (Standard for Binary Floating-Point Arithmetic), certain features are not supported even when using the strictfp
Strictfp
strictfp is a keyword in the Java programming language that restricts floating-point calculations to ensure portability. It was introduced into Java with the Java virtual machine version 1.2.-Basis:...
modifier, such as Exception Flags and Directed Roundings — capabilities mandated by IEEE Standard 754. Additionally, the extended precision floating-point types permitted in 754 and present in many processors are not permitted in Java.
HotSpot is a Java virtual machine for desktops and servers, maintained and distributed by Oracle Corporation. It features techniques such as just-in-time compilation and adaptive optimization designed to improve performance.-History:...
was implemented in Java 1.3 in 2000) there were many criticisms of performance. Java has been demonstrated to run at a speed comparable with optimised native code, and modern JVM implementations are regularly benchmarked as one of the fastest language platforms available -- typically within a factor of 3 relative to C/C++.
The performance of a compiled Java program will depend on how smartly its particular tasks are going to be managed by the host JVM, and how well the JVM takes advantage of the features of the hardware and OS in doing so. Thus, any Java performance test or comparison has to always report the...
has improved substantially since the early versions. Performance of JIT compilers relative to native compilers has in some optimized tests been shown to be quite similar.
Java bytecode is the form of instructions that the Java virtual machine executes. Each bytecode opcode is one byte in length, although some require parameters, resulting in some multi-byte instructions. Not all of the possible 256 opcodes are used. 51 are reserved for future use...
can either be interpreted at run time by a virtual machine, or it can be compiled at load time or runtime into native code which runs directly on the computer's hardware. Interpretation is slower than native execution, and compilation at load time or runtime has an initial performance penalty for the compilation. Modern performance JVM implementations all use the compilation approach, so after the initial startup time the performance is equivalent to native code.
Adobe Acrobat is a family of application software developed by Adobe Systems to view, create, manipulate, print and manage files in Portable Document Format . All members of the family, except Adobe Reader , are commercial software, while the latter is available as freeware and can be downloaded...
Adobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...
are among the most targeted software for security exploits. In 2010, targeting of Java security exploits increased significantly, resulting in Java becoming far more targeted than Acrobat or Flash.Microsoft publication This targeting appears to be tied to high numbers of computers with Java installed and the high percentage of computers that have not been updated with Java security updates.
Critics have suggested that updated versions of Java are not used because there is a lack of awareness by many users that Java is installed, there is a lack of awareness of many users of how to update Java, and (on corporate computers) many companies restrict software installation and are slow to deploy updates.
Among the suggestions made by critics is that users should consider uninstalling Java given the security risk and given the limited number of web sites that require Java to be installed on the browser's computer.
This is a comparison of the Java programming language with the C++ programming language.- Design aims :The differences between the C++ and Java programming languages can be traced to their heritage, as they have different design goals....
- Standardization :The two platforms, their programming libraries, their binary formats, and their runtime environments have largely been governed by very different means.The .NET platform as a whole has not been standardized...
The performance of a compiled Java program will depend on how smartly its particular tasks are going to be managed by the host JVM, and how well the JVM takes advantage of the features of the hardware and OS in doing so. Thus, any Java performance test or comparison has to always report the...
Richard Matthew Stallman , often shortened to rms,"'Richard Stallman' is just my mundane name; you can call me 'rms'"|last= Stallman|first= Richard|date= N.D.|work=Richard Stallman's homepage...
The free software movement is a social and political movement with the goal of ensuring software users' four basic freedoms: the freedom to run their software, to study and change their software, and to redistribute copies with or without changes. The alternative terms "software libre", "open...
