# To Load the terrJava Package

Prepare your system before you load the terrJava package. After your system is prepared, you can load the package by calling `library()`.

Before loading the terrJava package, you must set the `JAVA_HOME` environment variable to the base of the Java installation. This can be read within TERR with:

       Sys.getenv("JAVA_HOME")

If this is the empty string, set it to the directory where Java is installed with a call such as:

      Sys.setenv(JAVA_HOME="/usr/lib/jvm/java-7-sun/")

Alternatively, you can set the `JAVA_HOME` environment variable before starting TERR.

The terrJava package is included with the TERR built-in libraries. You can load it with:

      library(terrJava)

If the library loads without errors, you can test calling into Java by executing the following expressions, both of which should return the number 8:

      .JavaMethod("java/lang/Math", "pow", "(DD)D", 2, 3)
      .JavaMethod("com/tibco/terr/TerrJava", "testPow", "(DD)D", 2, 3)

## Example

The following example demonstrates setting the `JAVA_HOME` environment variable, starting TERR, loading the terrJava package, and running the tests on Linux:

    testlabl6406 ~% setenv JAVA_HOME /usr/lib/jvm/java-7-sun/
    testlabl6406 ~% TERR
    Cannot read termcap database; using dumb terminal settings.
    Cloud Software Group, Inc. Confidential Information
    Copyright (C) 2011-2024 Cloud Software Group, Inc. ALL RIGHTS RESERVED
    Spotfire Enterprise Runtime for R version 6.1.3 for Linux 64-bit
    Type 'help()' for help.
    Type 'q()' to quit.
    > library(terrJava)
    > .JavaMethod("java/lang/Math", "pow", "(DD)D", 2, 3)
    [1] 8
    > .JavaMethod("com/spotfire/terr/TerrJava", "testPow", "(DD)D", 2, 3)
    [1] 8