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Difference between revisions of "Java10/Examples"

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| compiler errors are shown
 
| compiler errors are shown
 
|-
 
|-
−
! colspan="3" | Editing with Ease: Completion for 'var'
+
! colspan="3" | Essential Utilities: Code Completion, Hover and Quick Fix.
 
|-
 
|-
 
! scope="row" | Basic context based var completion
 
! scope="row" | Basic context based var completion
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| completes var since the place is appropriate
 
| completes var since the place is appropriate
 
|-
 
|-
−
! scope="row" | Basic context based var completion
+
! scope="row" | Negative Case - no completion
 
|  
 
|  
−
<br>
 
 
<br>
 
<br>
 
<source lang="java">
 
<source lang="java">
Line 109: Line 108:
 
}
 
}
 
</source>
 
</source>
 +
<br>
 
[[File:var.nocomplete.jpg]]
 
[[File:var.nocomplete.jpg]]
 
| does not offer 'var' as completion
 
| does not offer 'var' as completion
−
|-
+
! scope="row" | Hover  
−
! colspan="3" | The Essential Utilities: Code Select, Hover, Navigate, Search and Rename
+
|  
−
|-
+
−
! scope="row" | Module Select & Hover
+
−
| <br>
+
−
In the module-info.java file of the first project, select <code>second</code> in the <code>requires second;</code> directive
+
 
<br>
 
<br>
−
<br>
 
−
[[File:Hover.jpg]]
 
−
| Hover appears
 
−
|-
 
−
! scope="row" | Module Select, Hover & Navigate
 
−
| In the above scenario, after hover appears, click on the navigate
 
−
| module-info.java file of second opened
 
−
|-
 
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! scope="row" | Module Select, & Search
 
−
| <br>
 
−
In the module-info.java file of the second project, select second in module declaration <code> module second {</code> and search for references
 
−
<br>
 
−
<br>
 
−
[[File:Modsearch2.jpg]]
 
−
| In the search view, the reference in directive <code>requires second;</code> in file first -> module-info.java is shown.
 
−
|-
 
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! scope="row" | Package Search
 
−
| <br>
 
−
create package <code>pack1</code> to the project first.
 
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<br>add <code>exports pack1;</code> directive in module-info.java file of first.
 
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<br>search for references of <code>pack1</code>
 
−
| In the search view, the reference of <code>pack1</code> in directive <code>exports pack1;</code> in file  first -> module-info.java is shown, similar to other <code>pack1</code> references if any
 
−
|-
 
−
! scope="row" | Type Search
 
−
| create Type <code>X</code> in  the project first, add directive <code>uses X;</code> in module-info.java file of first, and search for references of X
 
−
| In the search view, the reference of <code>X</code> in directive  <code>uses X;</code> in file first -> module-info.java is shown, similar to other <code>X</code> references if any
 
−
|-
 
−
! scope="row" |Code Select &  Rename
 
−
| in module-info.java file of first, select <code>X</code> in directive <code>uses X;</code> and rename to <code>X11</code>
 
−
| rename exhibits usual behavior - renames definition and references of <code>X</code> to <code>X11</code>
 
−
|-
 
−
! colspan="3" | The Outlier: Milling Project Coin Enhancements
 
−
|-
 
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! scope="row" | @Safevarargs
 
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| <code>@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
 
−
 
−
 
 
<source lang="java">
 
<source lang="java">
−
package packsafe;
+
package packvar;
−
import java.util.ArrayList;
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public class VarComplete {
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import java.util.List;
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  public static void main(String[] args) {
−
 
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String s = new String("hello");
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public class SafeVar {
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var x = s;
−
private int getLen(List<String>...list) {
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System.out.println(x);
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List<String>[] l = list;
+
  }
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return l.length;
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−
}
+
−
 
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public static void main(String[] args) {
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−
SafeVar x = new SafeVar();
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List<String> l = new ArrayList<>();
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−
int len = x.getLen(l); // Use Quick Assist of SafeVarargs here<br>
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System.out.println("Length:" + len);
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−
}
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−
}</source>
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−
| <code>@SafeVarargs</code> inserted before <code>getLen()</code> and the warnings go away
+
−
|-
+
−
! scope="row" | Effectively Final AutoCloseables
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| 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 <code> t1 = null; // Remove this code </code>.
+
−
 
+
−
 
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−
<source lang="java">package packtry;
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import java.io.Closeable;
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import java.io.IOException;
+
−
 
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class Two implements Closeable {
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@Override
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public void close() throws IOException {
+
−
// nothing
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−
}
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−
}
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public class TryStmtTwo {
+
−
 
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public void foo() throws IOException {
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Two t1 = new Two();
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−
try (t1; final Two t2 = new Two()) {
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−
// Empty by design
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−
}
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t1 = null; // Remove this code
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−
}
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public static void main(String[] args) {
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−
System.out.println("Done");
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−
}
+
 
}
 
}
 
</source>
 
</source>
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| Code without errors. For the more inquisitive, check the generated code to see that the close is generated for <code>t1</code> as well which is not a final variable but an effectively final variable.
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<br>
−
|-
+
[[File:var.hover.jpg]]
−
! scope="row" | Anonymous Diamond
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| shows javadoc of the type associated with var
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| 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.
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−
 
+
−
 
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−
<source lang="java">
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−
public class Dia {
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@SuppressWarnings("unused")
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public static void main(String[] args) {
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−
Y<?> y1 = new Y(){}; // Change this to new Y<>(){}
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−
}
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−
}
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class Y<T> {}
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</source>
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−
 
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| Diamond operator <code><></code> accepted and code compiles without warning
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−
|-
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! scope="row" | Illegal  Underscore
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| Underscore is an illegal identifier from Java 9 onwards. Uncomment the commented line in the following example
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−
 
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−
 
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<source lang="java">public class UnderScore {
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//Integer _ ;
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}
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</source>
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| error: "'_' should not be used as an identifier, since it is a reserved keyword from source level 1.8 on"
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−
|-
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! scope="row" | Private Methods
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| private interface methods are allowed. Change the <code>default</code> of worker to private
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−
 
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−
 
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−
<source lang="java">
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−
public interface I {
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default void worker() {}<
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−
 
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−
default void foo() {
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worker();
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−
}
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−
+
−
default void bar() {
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worker();
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−
}
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−
}
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−
</source>
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−
| Code compiles with <code>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.
+
 
|-
 
|-
−
! colspan="3" | Coming Soon to an Eclipse Version nearby you: The Java 9 DOM AST for module, Automatic Modules support, Quick Fixes and more...Watch this space for updates.
+
! colspan="3" | More to come in Java 11 !
 
|}
 
|}

Revision as of 12:55, 26 March 2018

ALPHA QUALITY NOW - EXPECTED TO BE COMPLETE BY : 1ST APRIL 2018

This is an informal page listing examples of features that are implemented by the Java 10 Support for Oxygen. You are welcome to try out these examples. If you find bugs, please file a bug after checking for a duplicate entry here.


Feature / Steps Expected Result
The Pre-requisite: Java 10 JRE Support
Add Java 10 JRE Use Eclipse Preferences -> Java -> Installed JREs -> Add

FileAddJ10.jpg

Java 10 JRE recognized as a valid JRE
Project JRE In Package Explorer Use Project Context Menu and add Java 10 JRE JRE specific (eg Object) gets resolved in the project.
Package Explorer Go to Package Explorer and expand the Java 10 JRE Modules (eg java.base etc) are listed in the package explorer view
The First Step: Java 10 Compliance
Set Project Compliance in Package Explorer Context Menu of Project -> Properties -> Set project-specific, drop down to 10



J10.compliance.jpg

No compiler errors
Basic Necessity : Compilation and Error Reporting
Positive Compilation Use the following code: 
package packvar;
 
import java.util.ArrayList;
import java.util.List;
 
public class VarUsage {
	public static void main(String[] args) {
		String s = new String("Hello World");
 
		var x = s; // var allowed in the variable declaration
		System.out.println(x);
 
		List<String> l = new ArrayList<>();
		l.add("List.Hello");
		for (var lx : l) { // var allowed in enhanced for loop
			System.out.println(lx);
		}
	}
}



Var.compile.jpg

code compiles
Compiler Error Cases 
package packvar;
 
public class VarError {
  public static void main(String[] args) {
    String s = new String("Hello");
    var x; // compiler error: Cannot use 'var' on variable without  initializer	
    var y = null; // compiler error: Cannot infer type for local variable initialized to 'null'	
  }
}
 compiler errors are shown
Essential Utilities: Code Completion, Hover and Quick Fix.
Basic context based var completion 



package packvar;
 
public class VarComplete {
  public static void main(String[] args) {
	String s = new String("hello");
 
	va // try completing here
}
}

Var.complete.jpg

completes var since the place is appropriate
Negative Case - no completion 


package packvar;
 
public class VarComplete {
	va // complete here - 'var' not offered as a completion candidate
}


Var.nocomplete.jpg

does not offer 'var' as completion Hover 


package packvar;
public class VarComplete {	
  public static void main(String[] args) {
	String s = new String("hello");
	var x = s;
	System.out.println(x);
  }
}


Var.hover.jpg

shows javadoc of the type associated with var
More to come in Java 11 !
Retrieved from "https://wiki.eclipse.org/index.php?title=Java10/Examples&oldid=424177"

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