Programming Java 7 in Eclipse

Question

I installed JDK 7 and Eclipse 3.6M6. Then, I added JRE 7 as a new JRE execution environment in Eclipse, and set the compiler compliance level to Java 7. I can compile the following piece of code through command line using the javac that comes with JDK 7.

import java.util.HashMap;
import java.util.Map;

public class Try {

    public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();
    }
}

But, Eclipse gives the following error messages.

Incorrect number of arguments for type HashMap; it cannot be parameterized with arguments Try.java /TryJava7/src line 7 Java Problem

Syntax error on token "<", ? expected after this token Try.java /TryJava7/src line 7 Java Problem

Even though I've set the compliance level of the compiler to Java 7, it looks like Eclipse doesn't understand Java7 syntax yet. Is it possible to play with Java 7 in Eclipse?

The following is the content of .classpath.

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
  <classpathentry kind="src" path="src"/>
  <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7"/>
  <classpathentry kind="output" path="bin"/>
</classpath>

And, the following is the content of .settings/org.eclipse.jdt.core.prefs.

eclipse.preferences.version=1
org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.7
org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
org.eclipse.jdt.core.compiler.compliance=1.7
org.eclipse.jdt.core.compiler.debug.lineNumber=generate
org.eclipse.jdt.core.compiler.debug.localVariable=generate
org.eclipse.jdt.core.compiler.debug.sourceFile=generate
org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
org.eclipse.jdt.core.compiler.source=1.7

Answer 1

Eclipse has its own embedded Java compiler. So if there is no eclipse beta or something like that that already can compile Java 7 then you're out of luck.

Netbeans should work.

Answer 2

As Alex pointed out, Eclipse uses its own compiler which currently doesn't support Java 7 and, as noted in the Project Plan For Eclipse Project, version Helios, support for Java 7 is deferred and decoupled from the 3.6 release:

• ( deferred) Add support for Java SE 7 features. The next feature release of Java SE is version 7, which will probably be available in the second half of 2010. While the contents of this release are still under discussion, that release is expected to contain extensions to the Java language, including annotations on types (JSR-308), modularity support (JSR-294), and other minor language changes (Coin project). Eclipse Java tooling will include initial support for compiling, editing, and launching applications for Java 7 for those parts which have publicly available specifications (only JSR-308 at this point). [JDT Core, JDT UI] (288548)

  NOTE: In order to align our schedule with the delayed official Java 7 appearance and due to lack of publicly available specifications (including lack of a Java 7 JSR), we have decided to move the development work to a separate branch and decouple it from the 3.6 release. In that branch we will continue to develop the Java 7 features as they become publicly accessible. We will deliver separate updates for the official builds in order to provide early access to Java 7 features.

Answer 3

I checkout the so called JSR 308 branch of org.eclipse.jdt.core using the following CVS repository information.

Connection type: pserver
User: anonymous
Host: dev.eclipse.org
Port: Default
Repository path: /cvsroot/eclipse
Module: org.eclipse.jdt.core
Tag: JSR_308 (Branch)

Then, I followed the instructions to install the checked out JDT in eclipse. Subsequently, I looked up org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NegativeTypeAnnotationTest.java and /org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/TestAll.java to come up with small examples exercising JSR 308 type annotations.

At this point, the branch supports and generates the corresponding new attributes in the .class files when annotations on types are present. But, annotation processors don't seem to work.