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− | === PAGE Nearing Completion - under construction ===
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| This is an informal page listing examples of features that are implemented by the Java 11 Support. You are welcome to try out these examples. If you find bugs, please file a bug after checking for a duplicate entry [https://bugs.eclipse.org/bugs/buglist.cgi?cmdtype=dorem&remaction=run&namedcmd=J11.Open&sharer_id=152344 here]. | | This is an informal page listing examples of features that are implemented by the Java 11 Support. You are welcome to try out these examples. If you find bugs, please file a bug after checking for a duplicate entry [https://bugs.eclipse.org/bugs/buglist.cgi?cmdtype=dorem&remaction=run&namedcmd=J11.Open&sharer_id=152344 here]. |
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| ! scope="row" | Basic Nesting Principles | | ! scope="row" | Basic Nesting Principles |
| | | | | |
− | Nestmate Concept: A JVM concept - All inner classes are now conceptually considered as one group.
| + | <b>Description: Nest Based Access - A JVM Concept.</b> |
− | This was already the case in Java Source, but JVM also now recognizes this.
| + | A top level class and all inner classes form a single unit for access, a "nest".JVM |
− | First step is that two new attributes have been added, NestHost and NestMember.
| + | specification added two attributes in the classfile NestHost and NestMember. The top |
− | The top most class will have the NestMember attribute listing all the members while | + | most class will have the NestMember attribute listing all the members while each of |
− | each of the inner classes will have a NestHost attribute listing the top level class. | + | the inner classes will have a NestHost attribute listing the top level class. Using |
− | Using this, some of the synthetic bridge methods are elided transparent to the programmer. | + | this, some of the synthetic bridge methods are elided transparent to the programmer. |
− | Note that this feature is relevant only for tools that process byte code and hence, in general, | + | Note that this feature is relevant only for tools that process byte code and hence, |
− | this feature would be "transparent" to a "normal" programmer. This feature is applicable for byte | + | in general, this feature would be "transparent" to a "normal" programmer. This feature |
− | code processors, for eg our Disassembler has been enhanced to show these attributes. | + | is applicable for byte code processors, for eg our Disassembler has been enhanced to |
− | <br>
| + | show these attributes. For further info please read JEP 181. |
− | <br>
| + | |
| <br> | | <br> |
| <source lang="java"> | | <source lang="java"> |
This is an informal page listing examples of features that are implemented by the Java 11 Support. You are welcome to try out these examples. If you find bugs, please file a bug after checking for a duplicate entry here.
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Feature / Steps
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Expected Result
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The Pre-requisite: Java 11 JRE Support
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Add Java 11 JRE
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Use Window -> Preferences-> Java -> Installed JREs -> Add...
[note: Eclipse -> Preferences in Mac / Window -> Preferences in Windows]
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Java 11 JRE recognized as a valid JRE
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Project JRE
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In Package Explorer Use project's context menu and add Java 11 JRE |
JRE specific (eg Object) gets resolved in the project.
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Package Explorer
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Go to Package Explorer and expand the Java 11 JRE |
Modules (eg java.base etc) are listed in the package explorer view
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The First Step: Java 11 Compliance
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Set Project Compliance in Package Explorer
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Context Menu of Project -> Properties -> Set project-specific, drop down to 11
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11 is shown in the drop down list
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Basic Necessity : Compilation and Error Reporting
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Positive Compilation
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Use the following code:
package pack1;
public class VarLambda {
public static void main(String[] args) {
I lam = (var x) -> { // var compiles here
System.out.println(x);
};
lam.apply(20);
}
}
interface I {
public void apply(Integer k);
}
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Code compiles
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Compiler Error Case 1
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package pack1;
public class VarLambdaErr {
public static void main(String[] args) {
I lam = (var x, z) -> { // should not mix with type-elided params
System.out.println(x);
};
lam.apply(20);
}
}
interface I {
public void apply(Integer k, Integer z);
}
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Compiler errors are shown
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Compiler Error Case 2
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package pack1;
public class VarLambdaErr {
public static void main(String[] args) {
I lam = (var x, Integer z) -> { // should not mix with non-var params
System.out.println(x);
};
lam.apply(20, 200);
}
}
interface I {
public void apply(Integer k, Integer z);
}
|
Compiler errors shown
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Hover and Navigation
|
Hover
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Use the following code:
package pack1;
public class VarLambda {
public static void main(String[] args) {
I lam = (var x) -> {
System.out.println(x);
};
lam.apply(20);
}
}
interface I {
public void apply(Integer k);
}
|
Hover and Navigation
|
Nestmates
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Basic Nesting Principles
|
Description: Nest Based Access - A JVM Concept.
A top level class and all inner classes form a single unit for access, a "nest".JVM
specification added two attributes in the classfile NestHost and NestMember. The top
most class will have the NestMember attribute listing all the members while each of
the inner classes will have a NestHost attribute listing the top level class. Using
this, some of the synthetic bridge methods are elided transparent to the programmer.
Note that this feature is relevant only for tools that process byte code and hence,
in general, this feature would be "transparent" to a "normal" programmer. This feature
is applicable for byte code processors, for eg our Disassembler has been enhanced to
show these attributes. For further info please read JEP 181.
public class X {
private class A {
class B {}
}
private class Y extends A {
}
}
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In X.class (Disassembled)
Nest Members:
#21 X$A,
#24 X$A$B,
#27 X$Y
In each of X$A, X$A$B, X$Y the attribute:
Nest Host: #22 X
|