http://www.oracle.com/technetwork/java/javase/downloads/index.html.
Java is available as both 32-bit and 64-bit binaries. Deciding which one to download can be complex, see 32-bit or 64-bit.
Ptolemy II 10.0 requires Java 1.6 (also known as Java 6) or later because ptdb uses javax.swing.GroupLayout. Also, Java 1.5 is past its end of life. Java 1.7 (also known as Java 7) and Java 1.8 will work.
The development version available via svn is best built with Java 1.8. See below for details.
In January, 2015, the core of development version can be build with Java 1.6 by running configure, but this is not supported or tested. Over time, Java 1.6 is less likely to work.
The full development version of Ptolemy II requires Java 1.7 because particleFiltering uses type inference for generic instance creation and catches multiple exceptions. Over time, more and more code will require Java 1.7 and Java 1.8.
Note that the core of Ptolemy that is used by Kepler can be built with Java 1.7. To use Java 1.7 would require excluding ptolemy/actor/lib/jjs and org/ptolemy/machineLearning. The core of Ptolemy II is built using Java 1.7 on a nightly basis as part of the Kepler build.
The development version of Ptolemy II requires Java 1.8 to use Nashorn in ptolemy/actor/lib/jjs and IntStream in org/ptolemy/machineLearning. Over time, more and more code will require Java 1.8. The
$PTII/build.default.xmlworks best with Java 1.8The Oracle (formerly Sun) Java Development Kit (JDK) is preferred.
The IBM JDK will work under Linux.
OpenJDK may work with Ptolemy II, but could have problems with Kepler.
After installing Java, then the next step is to install Eclipse.