This Specification defines version 13 of the Java Platform, Standard Edition (“Java SE 13”). The Reference Implementation of this Specification is the Java Development Kit, version 13 (“JDK 13”).
Changes to this document since DRAFT 1 are indicated by green changebars in the right margin, as illustrated by this text.
|4||Component JSR Specifications|
|8||APIs proposed for removal|
|A1||Complete API Specification|
|A2||API Specification differences|
|A3||Java Language & Virtual Machine Specifications|
This release continues the evolution of the Platform to ensure the broadest possible success of the core Java technology.
This document directly specifies API features, enhancements, clarifications, and bug fixes. It also specifies features by reference to other Specifications which are revised in Maintenance Releases of existing JSRs. The specifications of these changes are contained in two accompanying documents: Annex 1 is the complete Java SE 13 API Specification and Annex 2 is an annotated API specification showing the exact differences relative to the Final Release of Java SE 12. Informative background for these changes may be found in the list of approved Change Specification Requests for this release.
This Specification includes the Java SE 13 Editions of The Java Language Specification and The Java Virtual Machine Specification in Annex 3. The Java SE 13 Editions contain all corrections and clarifications made since the Java SE 12 Editions, as well as additions for new features.
The Final Release of this Specification is expected to include all of the currently described features and updates; however, further changes may be forthcoming. For example, the Expert Group could determine that a feature is not yet be ready for standardization.
Changes to the Java SE Platform Specification are categorized as either features or enhancements. A feature is, roughly speaking, a change of which at least one of the following statements is true:
Any addition that is not a feature is considered an enhancement.
There is, obviously, room for judgment when interpreting this definition. In order to maximize the visibility of Platform revisions we generally tend to consider borderline items to be features rather than enhancements.
Some Component JSR Specifications previously incorporated into the Platform are still available separately or have significant Specifications themselves. Changes to their Specifications are therefore made in separate Maintenance Releases, which are incorporated here by reference:
Each Component JSR Specification, or revision thereto, may be related to one or more features in the detailed list below.
Work on features in the Java SE 13 Reference Implementation is organized in terms of JDK Enhancement Proposals (JEPs). Each feature description gives a link to the corresponding JEP document as a convenience, but that document is not a normative part of this Specification. Some features are included in the Java SE 13 Reference Implementation on a preview basis, to gain exposure before achieving permanent status in a later release of the Java SE Platform.
switch so it can be used as either a statement or an expression, and so that both forms can use either traditional
case ... : labels (with fall through) or new
case ... -> labels (with no fall through), with a further new statement for yielding a value from a
switch expression. These changes will simplify everyday coding, and prepare the way for the use of pattern matching (JEP 305) in
switch. This will be a preview language feature.
Add text blocks to the Java language. A text block is a multi-line string literal that avoids the need for most escape sequences, automatically formats the string in a predictable way, and gives the developer control over format when desired. This will be a preview language feature.
Preview features A preview language or VM feature is a new feature of the Java SE Platform that is fully specified, fully implemented, and yet impermanent. This Specification incorporates the Java SE 12 Platform Specification (JSR 386), subsection Preview features by reference.
A module is a named set of packages designed for reuse. A specification governed by the JCP defines standard packages, and may group them into one or more standard modules.
This Specification groups the standard packages of the Java SE Platform into 21 standard modules, which we refer to as the Java SE modules. The name of a Java SE module always starts with the string "java.". The complete list of such modules is:
Compared to Java SE 12, this Specification does not add or remove any modules.
The module graph The Java SE modules depend upon each other as stated in their specifications, which are part of the overall API Specification. The corresponding complete Java SE module graph has too many edges to be displayed easily in visual form; here is the transitive reduction of the directed acyclic graph, in which redundant edges are omitted (click to enlarge):
Here is how to read this visualization of the module graph:
If one module depends upon another, and it grants implied readability to that module via a requires transitive directive, then there is an edge from the first module to the second.
At the very bottom is the java.base module, which contains essential classes such as java.lang.Object and java.lang.String. The base module depends upon no module, and every other module depends upon the base module.
At the top is the java.se module, which gathers together all of the modules that comprise the Java SE Platform. This is an example of an aggregator module, which logically gathers the content of other modules by granting implied readability to them, but adds no content of its own. A run-time system configured to contain the java.se module will contain all of the packages of the Java SE Platform.
A module is a Java SE module — that is, considered part of the Java SE Platform Specification — if and only if it is a standard module reachable from the java.se module.
Following the conventions established by the Enhanced Deprecation feature,
various modules and APIs were annotated with
forRemoval=true in the “APIs
Proposed for Removal” section of the Platform Specifications for
Java SE 9,
Java SE 10,
Java SE 11, and
Java SE 12.
The following individual APIs are removed from this Specification. The number in parentheses indicates the Java SE Platform Specification which first proposed their removal.
The following APIs were proposed for removal by the Platform Specifications for Java SE 9, Java SE 10, and Java SE 11, and continue to be eligible for removal in a future release. They are not removed from this Specification.
Finally, the following APIs are annotated as
forRemoval=true in this Specification. This makes them
eligible for removal in a future release of the Platform.
Compared to Java SE 12, this Specification does not add or propose to remove any further APIs.