Java Programming Language Enhancements
- Binary Literals -
In Java SE 7, the integral types (
byte, short, int, and long) can also be expressed using the binary number system. To specify a binary literal, add the prefix 0b or 0B to the number.
- Underscores in Numeric Literals -
Any number of underscore characters (
_) can appear anywhere between digits in a numerical literal. This feature enables you, for example, to separate groups of digits in numeric literals, which can improve the readability of your code.
- Strings in switch Statements -
You can use the
String class in the expression of a switch statement.
- Type Inference for Generic Instance Creation -
You can replace the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (
<>) as long as the compiler can infer the type arguments from the context. This pair of angle brackets is informally called the diamond.
- Improved Compiler Warnings and Errors When Using Non-Reifiable Formal Parameters with Varargs Methods -
The Java SE 7 complier generates a warning at the declaration site of a varargs method or constructor with a non-reifiable varargs formal parameter. Java SE 7 introduces the compiler option
-Xlint:varargs and the annotations @SafeVarargs and @SuppressWarnings({"unchecked", "varargs"}) to supress these warnings.
- The try-with-resources Statement -
The
try-with-resources statement is a try statement that declares one or more resources. A resource is an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Any object that implements the new java.lang.AutoCloseable interface or the java.io.Closeable interface can be used as a resource. The classes java.io.InputStream, OutputStream, Reader, Writer, java.sql.Connection, Statement, and ResultSet have been retrofitted to implement the AutoCloseable interface and can all be used as resources in a try-with-resources statement.
- Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking -
A single
catch block can handle more than one type of exception. In addition, the compiler performs more precise analysis of rethrown exceptions than earlier releases of Java SE. This enables you to specify more specific exception types in the throws clause of a method declaration.
No language changes were introduced in Java SE 6.
- Generics - This long-awaited
enhancement to the type system allows a type or method to operate
on objects of various types while providing compile-time type
safety. It adds compile-time type safety to the Collections
Framework and eliminates the drudgery of casting. See the Generics lesson in the Java Tutorials. (JSR
14)
- Enhanced
for
Loop - This new language construct eliminates the drudgery
and error-proneness of iterators and index variables when iterating
over collections and arrays. (JSR 201)
- Autoboxing/Unboxing - This
facility eliminates the drudgery of manual conversion between
primitive types (such as int) and wrapper types (such as Integer).
(JSR 201)
- Typesafe Enums - This flexible
object-oriented enumerated type facility allows you to create
enumerated types with arbitrary methods and fields. It provides all
the benefits of the Typesafe Enum pattern (Effective Java, Item 21) without the verbosity and the error-proneness. (JSR 201)
- Varargs - This facility
eliminates the need for manually boxing up argument lists into an
array when invoking methods that accept variable-length argument
lists.
- Static Import - This
facility lets you avoid qualifying static members with class names
without the shortcomings of the "Constant Interface antipattern."
(JSR 201)
- Annotations (Metadata) -
This language feature lets you avoid writing boilerplate code under
many circumstances by enabling tools to generate it from
annotations in the source code. This leads to a "declarative"
programming style where the programmer says what should be done and
tools emit the code to do it. Also it eliminates the need for
maintaining "side files" that must be kept up to date with changes
in source files. Instead the information can be maintained
in the source file. (JSR 175)
NOTE: The @Deprecated annotation provides a way to
deprecate program elements. See How and When To Deprecate
APIs.
Generics papers
- JSR14: Adding Generic Types to the Java Programming Language
- Making
the Future Safe for the Past: Adding Genericity to the Java
Programming Language (PDF)
Bracha, Odersky, Stoutamire, and Wadler. OOPSLA 98, Vancouver,
October 1998. ( other
formats)
-
GJ: Extending the Java Programming Language with Type
Parameters (PDF)
Bracha, Odersky, Stoutamire, and Wadler. A tutorial on GJ. August
1998. ( other
formats)
-
Adding Generics to the Java Programming Language (PDF)
Bracha. Slides from JavaOne 2003 presentation.
- Adding Wildcards
to the Java Programming Language (PDF)
Torgersen, Hansen, Ernst, Ahe, Bracha and Gafter. An ACM paper,
2004.
- Assertion Facility - Assertions are
boolean expressions that the programmer believes to be true
concerning the state of a computer program. For example, after
sorting a list, the programmer might assert that the list is in
ascending order. Evaluating assertions at runtime to confirm their
validity is one of the most powerful tools for improving code
quality, as it quickly uncovers the programmer's misconceptions
concerning a program's behavior.
