{"id":3947,"date":"2017-08-10T13:46:34","date_gmt":"2017-08-10T11:46:34","guid":{"rendered":"http:\/\/www.tutego.de\/blog\/javainsel\/?p=3947"},"modified":"2017-08-10T13:46:34","modified_gmt":"2017-08-10T11:46:34","slug":"was-eclipse-bisher-bei-java-9-untersttzt","status":"publish","type":"post","link":"https:\/\/www.tutego.de\/blog\/javainsel\/2017\/08\/was-eclipse-bisher-bei-java-9-untersttzt\/","title":{"rendered":"Was Eclipse bisher bei Java 9 unterstützt"},"content":{"rendered":"

Siehe https:\/\/wiki.eclipse.org\/Java9\/Examples<\/a><\/p>\n

Feature<\/b> \/ Steps
Expected Result<\/p>\n

The Pre-requisite: Java 9 JRE Support<\/p>\n

Add Java 9 JRE
Use Eclipse Preferences -> Java -> Installed JREs -> Add<\/p>\n

\"Addj9.jpg\"<\/a><\/p>\n

Java 9 JRE recognized as a valid JRE<\/p>\n

Project JRE
In Package Explorer Use Project Context Menu and add Java 9 JRE
JRE specific (eg Object) gets resolved in the project.<\/p>\n

Package Explorer
Go to Package Explorer and expand the Java 9 JRE
Modules (eg java.base etc) are listed in the package explorer view<\/p>\n

The First Step: Module Creation<\/p>\n

Manual
Context Menu of src -> New -> File – give the module-info.java as name
no compiler errors<\/p>\n

Automatic
Context Menu of Project -> Cofigure -> Create module-info. <\/p>\n

\"AutomoduleCreate.jpg\"<\/a><\/p>\n

A default module-info.java with all packages exported should be created<\/p>\n

Basic Necessity : Compilation, Module Dependency & Error Reporting<\/p>\n

Unspecified Dependency
create projects "first" and "second" and create module-info.java files in each of giving the module names "first" and "second" respectively.<\/p>\n

In the first module add the directive requires second; <\/code>. This initial configuration would look something similar to the one shown in the figure.
\"Initmods.jpg\"<\/a><\/p>\n

Compiler gives error "second cannot be resolved to a module"<\/p>\n

Define Dependency
In the above scenario, add Project second as a dependent project for project first
Compiler error goes away<\/p>\n

Duplicate Dependency
Continuing from the above scenario, add a duplicate requires second;<\/code> directive in the module-info.java file of the first
Compiler gives error "Duplicate requires entry: second"<\/p>\n

Circular Dependency
add a circular dependency ie <\/p>\n

add second project dependent on first
add requires first;<\/code> directive in the module-info.java file of the second project ie replace \/\/ empty by design<\/code> comment by this directive<\/p>\n

Two compiler errors " Cycle exists in module dependencies, Module second requires itself via first"<\/p>\n

Editing with Ease: Completion in module-info.java file<\/p>\n

Keyword Completion (1)
In the module-info.java file of say second project, after module first {<\/code>, press completion key (for eg, ctrl+space in windows) <\/p>\n

\"Keycomplete1.jpg\"<\/a><\/p>\n

keywords exports<\/code>, opens<\/code>, requires<\/code>, provides<\/code> and uses<\/code> shown<\/p>\n

Keyword Completion (2)
after exports packagename<\/code>, or opens packagename<\/code> press completion key
keyword to is shown as an option<\/p>\n

Package Completion
after exports<\/code>, opens<\/code>, provides<\/code> or uses<\/code>, press completion key
package completion shown.<\/p>\n

Type Reference Completion
after exports<\/code>, opens<\/code>, provides<\/code> or uses<\/code>, or optionally after a dot after a package, ie exports packagename.<\/code> press completion key
Type completion shown.<\/p>\n

Implementation TypeRef Completion
after provides typename with<\/code> press completion key
Type completion shown and these typereferences are implementations of the type given before with.<\/p>\n

The Essential Utilities: Code Select, Hover, Navigate, Search and Rename<\/p>\n

Module Select & Hover<\/p>\n

In the module-info.java file of the first project, select second<\/code> in the requires second;<\/code> directive
\"Hover.jpg\"<\/a><\/p>\n

Hover appears<\/p>\n

Module Select, Hover & Navigate
In the above scenario, after hover appears, click on the navigate
module-info.java file of second opened<\/p>\n

Module Select, & Search<\/p>\n

In the module-info.java file of the second project, select second in module declaration module second {<\/code> and search for references
\"Modsearch2.jpg\"<\/a><\/p>\n

In the search view, the reference in directive requires second;<\/code> in file first -> module-info.java is shown.<\/p>\n

Package Search<\/p>\n

create package pack1<\/code> to the project first.
add exports pack1;<\/code> directive in module-info.java file of first.
search for references of pack1<\/code><\/p>\n

In the search view, the reference of pack1<\/code> in directive exports pack1;<\/code> in file first -> module-info.java is shown, similar to other pack1<\/code>references if any<\/p>\n

Type Search
create Type X<\/code> in the project first, add directive uses X;<\/code> in module-info.java file of first, and search for references of X
In the search view, the reference of X<\/code>in directiveuses X;<\/code> in file first -> module-info.java is shown, similar to other X<\/code>references if any<\/p>\n

Code Select & Rename
in module-info.java file of first, select X<\/code> in directive uses X;<\/code> and rename to X11<\/code>
rename exhibits usual behavior – renames definition and references of X<\/code>to X11<\/code><\/p>\n

The Outlier: Milling Project Coin Enhancements<\/p>\n

@Safevarargs
@SafeVarargs<\/code> is now allowed on private instance methods. There is even a support of quick assist for that. Use the following code which has warnings, and use the quick assist at the point mentioned in the comment <\/p>\n

package packsafe;\nimport java.util.ArrayList;\nimport java.util.List;   public class SafeVar {\n\tprivate int getLen(List<String>...list) {\n\t\tList<String>[] l = list;\n\t\treturn l.length;\n\t}   public static void main(String[] args) {\n\t\tSafeVar x = new SafeVar();\n\t\tList<String> l = new ArrayList<>();\n\t\tint len = x.getLen(l); \/\/ Use Quick Assist of SafeVarargs here<br>\n\t\tSystem.out.println("Length:" + len);\n\t}\n}<\/pre>\n
@SafeVarargs<\/code>inserted before getLen()<\/code> and the warnings go away<\/p>\n
Effectively Final Autoloseables
\n  
Effectively-final variables are allowed to be used as resources in the try-with-resources statement. The code below has an error. Try removing the line t1 = null; \/\/ Remove this code <\/code>. <\/p>\n
package packtry;\nimport java.io.Closeable;\nimport java.io.IOException;   class Two implements Closeable {\n\t@Override\n\tpublic void close() throws IOException {\n\t\t\/\/ nothing\n\t}\n}\npublic class TryStmtTwo {   public void foo() throws IOException {\n\t\tTwo t1 = new Two();\n\t\ttry (t1; final Two t2 = new Two()) {\n\t\t\/\/ Empty by design\n\t}\n\tt1 = null; \/\/ Remove this code\n\t}\n\tpublic static void main(String[] args) {\n\t\tSystem.out.println("Done");\n\t}\n}<\/pre>\n
Code without errors. For the more inquisitive, check the generated code to see that the close is generated for t1<\/code> as well which is not a final variable but an effectively final variable.<\/p>\n
Anonymous Diamond
\n  
In the following code, there is a warning about Y being a raw type and need to be parameterized. with Java 9 support, just add a diamond operator after Y. <\/p>\n
public class Dia {\n@SuppressWarnings("unused")\n\tpublic static void main(String[] args) {\n\t\tY<?> y1 = new Y(){}; \/\/ Change this to new Y<>(){}\n\t}\n}\nclass Y<T> {}<\/pre>\n
Diamond operator <><\/code>accepted and code compiles without warning<\/p>\n
Illegal Underscore
\n  
Underscore is an illegal identifier from Java 9 onwards. Uncomment the commented line in the following example <\/p>\n
public class UnderScore {\n\t\/\/Integer _ ;\n}<\/pre>\n
error: "’_‘ should not be used as an identifier, since it is a reserved keyword from source level 1.8 on"<\/p>\n
Private Methods
\n  
private interface methods are allowed. Change the default<\/code> of worker to private <\/p>\n
public interface I {\n\tdefault void worker() {}<   default void foo() {\n\t\tworker();\n\t}   default void bar() {\n\t\tworker();\n\t}\n}<\/pre>\n
Code compiles with private<\/code>as well. Note that this is a useful feature if two default methods wants to share the worker code and does not want the worker to be an public interface method.<\/p>\n","protected":false},"excerpt":{"rendered":"
Siehe https:\/\/wiki.eclipse.org\/Java9\/Examples Feature \/ Steps Expected Result The Pre-requisite: Java 9 JRE Support Add Java 9 JRE Use Eclipse Preferences -> Java -> Installed JREs -> Add Java 9 JRE recognized as a valid JRE Project JRE In Package Explorer Use Project Context Menu and add Java 9 JRE JRE specific (eg Object) gets resolved […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[7,85],"tags":[8],"class_list":["post-3947","post","type-post","status-publish","format-standard","hentry","category-entwicklungsumgebung","category-java-9","tag-eclipse"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/posts\/3947","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/comments?post=3947"}],"version-history":[{"count":1,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/posts\/3947\/revisions"}],"predecessor-version":[{"id":3948,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/posts\/3947\/revisions\/3948"}],"wp:attachment":[{"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/media?parent=3947"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/categories?post=3947"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tutego.de\/blog\/javainsel\/wp-json\/wp\/v2\/tags?post=3947"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}