Reliable Penguin

alternatives --verbose \
  --install /usr/bin/java  java \
    /usr/local/j2sdk1.4.2_04/bin/java 10 \
  --slave /usr/bin/rmiregistry rmiregistry \
    /usr/local/j2sdk1.4.2_04/bin/rmiregistry \
  --slave /usr/share/man/man1/rmiregistry.1 rmiregistry.1 \
    /usr/local/j2sdk1.4.2_04/man/man1/rmiregistry.1

alternatives --set java /usr/local/j2sdk1.4.2_04/bin/java

alternatives --verbose \
  --install /usr/bin/javac javac \
    /usr/local/j2sdk1.4.2_04/bin/javac 10 \
  --slave /usr/bin/jar jar \
    /usr/local/j2sdk1.4.2_04/bin/jar \
  --slave /usr/bin/rmic rmic \
    /usr/local/j2sdk1.4.2_04/bin/rmic \
  --slave /usr/share/man/man1/jar.1 jar.1 \
    /usr/local/j2sdk1.4.2_04/man/man1/jar.1 \
  --slave /usr/share/man/man1/rmic.1 rmic.1 \
    /usr/local/j2sdk1.4.2_04/man/man1/rmic.1

alternatives --set javac /usr/local/j2sdk1.4.2_04/bin/javac