Comment 3 for bug 68623

I've solved the problem by installing sun-java5-jdk.
sun-java5-jdk provides: java-compiler, java2-compiler

To get back to a clean system I tried to deinstall all java / eclipse /pydev related packages using:

sudo apt-get autoremove eclipse-pydev sun-java5-jre

As per your request:
sudo apt-get install eclipse-platform:

The following extra packages will be installed:
  ant eclipse-rcp java-common libbcel-java libcommons-beanutils-java
  libcommons-collections-java libcommons-collections3-java
  libcommons-dbcp-java libcommons-digester-java libcommons-el-java
  libcommons-launcher-java libcommons-logging-java libcommons-modeler-java
  libcommons-pool-java libjsch-java liblog4j1.2-java liblucene-java
  liblucene-java-doc libmx4j-java libregexp-java libservlet2.4-java
  libswt3.2-gtk-java libswt3.2-gtk-jni libtomcat5.5-java
Suggested packages:
  ant-doc eclipse-jdt eclipse-pde equivs libbcel-java-doc
  libcommons-beanutils-java-doc libcommons-collections-java-doc
  libcommons-collections3-java-doc liblogkit-java libavalon-framework-java
  libgnumail-java tomcat4 tomcat5 jython tomcat5.5
Recommended packages:
  ant-optional jikes java-compiler eclipse-platform-gcj eclipse
  eclipse-rcp-gcj libswt3.2-gtk-gcj
The following NEW packages will be installed:
  ant eclipse-platform eclipse-rcp java-common libbcel-java
  libcommons-beanutils-java libcommons-collections-java
  libcommons-collections3-java libcommons-dbcp-java libcommons-digester-java
  libcommons-el-java libcommons-launcher-java libcommons-logging-java
  libcommons-modeler-java libcommons-pool-java libjsch-java liblog4j1.2-java
  liblucene-java liblucene-java-doc libmx4j-java libregexp-java
  libservlet2.4-java libswt3.2-gtk-java libswt3.2-gtk-jni libtomcat5.5-java
0 upgraded, 25 newly installed, 0 to remove and 0 not upgraded.

I see no java compiler there!

Also with:
sudo apt-get install eclipse-platform-gcj

No compiler!
java-compiler is recommended, but not installed.

sudo apt-get install java-compiler:

Package java-compiler is a virtual package provided by:
  sun-java5-jdk 1.5.0-08-0ubuntu1
  jikes-sun 0.9
  j2sdk1.4 1.4.2.02-1ubuntu3
  kaffe-pthreads 2:1.1.7-4
  kaffe-jthreads 2:1.1.7-4
  jikes-sablevm 1.13-1
  jikes-kaffe 2:1.1.7-4
  jikes-gij 1:1.22-4
  jikes-classpath 2:0.92-3
  eclipse-ecj-gcj 3.1.2-3ubuntu1
  eclipse-ecj 3.1.2-3ubuntu1
  gcj-4.1 4.1.1-14ubuntu7
  gcj 4:4.1.1-6ubuntu3
You should explicitly select one to install.

It seems that the developers really want to force the user to choose his/her own java-compiler.

I'm not sure if I answered all your questions, please let me know if you need to know anything else.