Language
new @delegate: use-site target for annotation (e.g. @delegate:Transient)
private top-level Kotlin classes should be compiled to package private java classes
unfinished multiline comment is an error
previously deprecated language constructs are now errors
type ckecking for use-site variance fixed
generic functions are compared for specificity through solving a constraint system
having multiple vararg parameters for one function is prohibited
super-calls to functions with default parameters are prohibited (pass all arguments explicitly)
implicit receiver behavior fixed
as-import removes original names if they were imported before
user code is not allowed in kotlin.** packages
type parameters of extension properties allowed to be indirectly used by the receiver type
members of private classes can-not be accessed from non-private inline functions
Java interop
forEach from Kotlin's library is preferred to forEach from java.lang.Iterable
synthesized declarations (like JavaBeans properties and SAM-converted methods) are now resolved on par with members
support added for Java setters that return values
previously depreacted Java declarations removed from generated code
private setters allowed for lateinit properties
wildcards are not generated for redundant type projections (use List<@JvmWildcard Foo> instead of List
@Nullable/@NotNull annotations from different standard Java packages recognized (javax.annotations, Guava, Android, etc)
Standard Library
diagnostics for multiple conflicting Kotlin runtime versions in classpath
some functions have been made inline
many inline functions (most of them one-liners) can no longer be called from Java code. This will help us reduce the size of the runtime library in the future.
library code rearranged into more granular packages (no source changes should be required)
associate and associateBy are added to aid construction of maps associate and associateBy (instead of toMap/toMapBy)
groupBy with key- and value-selector functions
Map.getOrElse() and Map.getOrPut() now treat keys associated with null values as missing.
Map.getOrImplicitDefault() has been made internal
mutableListOf, mutableSetOf, mutableMapOf added to construct mutable collections. linkedListOf is deprecated
toMutableList added instead of toArrayList. The latter is deprecated
kotlin.system.exitProcess instead of System.exit
File.deleteRecursively only returns false in case of incomplete deletion
File.copyRecursively allows overwriting by specifying argument overwrite=true
changed File.copyTo behavior to be like Files.copy from JDK8.
more specific return type for File.inputStream, File.outputStream, String.byteInputStream.
IO utility functions taking charset name as a string are deprecated, use ones with Charset parameter.
File.useLines and Reader.readLines are introduced
File.(buffered)reader/writer now return less specific InputStreamReader/OutputStreamWriter and use UTF-8 encoding by default
Sequence and Iterable SAM constructor-like functions
Comparator- and comparison-related functions are moved to kotlin.comparisons package (not imported by default)
new properties in MatchResult: groupValues and destructured -- provided for easier handling of regular expression match results
Lazy is now an interface open for implementation
kotlin.system.measureTimeNano renamed to measureNanoTime.
plusElement and minusElement functions as a synonyms for list + element and list - element.
kotlin.test.assertFailsWith with Class
toLinkedMap is deprecated.
UTF_32 charset properties added to Chatsets
Tools
To enable Android Extensions, use: apply plugin: 'kotlin-android-extensions'
IDE
Intention to replace iteration over map entries with a loop using a destructuring declaration
Inspection and quickfix to cleanup redundant visibility modifiers
Inspection to replace 'assert' calls checking that a variable is not null with !! or ?: error(...)
Show "Kotlin not configured" notification when opening a .kt file in the IDE if the Kotlin runtime is not configured for the corresponding module
Action to generate the toString() method
Support for implementing members by primary constructor parameters
Parameter info popup works for showing type parameters
Completion offers name variants based on unresolved identifiers in current file
Quickfix for adding missing branches to a when expression
Support for moving nested classes to the upper level or into another top-level class
@Suppress now works for IDE inspections
Kotlin 是一个基于 JVM 的新的编程语言，由 JetBrains 开发。
其主要设计目标：
创建一种兼容Java的语言
让它比Java更安全，能够静态检测常见的陷阱。如：引用空指针
让它比Java更简洁，通过支持variable type inference，higher-order functions (closures)，extension functions，mixins and first-class delegation等实现。
让它比最成熟的竞争对手Scala语言更加简单。
软件详情：http://blog.jetbrains.com/kotlin/2016/02/kotlin-1-0-release-candidate-is-out/
下载地址：https://plugins.jetbrains.com/plugin/download?pr=&updateId=23813
来自:开源中国社区