loadeR.java

Java stuff on which other java-based R packages depend.

JVM Memory Configuration:

If the Java Virtual Machine (JVM) is already initialized (e.g., by another package), the memory configuration cannot be changed, and a warning will be shown. If the JVM has not yet been initialized and the user has already set a -Xmx value, it will be respected only if it is greater than 2 GB; otherwise, it will be automatically increased to 2 GB. In all cases, once the JVM is initialized, the actual maximum available memory will be reported. To override the default memory setting, set java.parameters before loading the package:

options(java.parameters = "-Xmx4g") # Set maximum heap space to 4 GB
library(loadeR.java)

Configuring netCDF-Java classpath

By default, loadeR.java will use netCDF-Java JARs found in the java package directory. Users can point to their own netCDF-Java classpath, using a netCDF-Java library installation.

loadeR.java provides options for defining the netCDF-Java classpath, which are considered in the following order of precedence:

1. R option: loadeR.java_classpath
2. Environment variable: LOADER_JAVA_CLASSPATH
3. Bundled fallback: java package directory

Each method accepts one or more classpath entries, separated by the platform path separator (: on Linux/macOS, ; on Windows). Wildcards (*) are supported. In the case of using *, the order of precedence within the same option follows lexicographic order (ascending).

Example: R option

options(loadeR.java_classpath = "/opt/netcdf-java/netcdfAll-5.9.0.jar")
library(loadeR.java)

Example: Environment variable

# Linux/macOS
export LOADER_JAVA_CLASSPATH="/opt/netcdf-java/lib/*"
R -q -e "library(loadeR.java)"

# Windows PowerShell
$env:LOADER_JAVA_CLASSPATH = "C:\netcdf-java\lib\*"
R -NoSave -e "library(loadeR.java)"

Bundled fallback

• Drop any required JARs into the java package directory.

Configuring netCDF-Java version

On startup, loadeR.java tries to detect the netCDF-Java version from the JAR’s MANIFEST.MF file.

If no MANIFEST.MF is found, the version cannot be detected automatically. You can manually set the netCDF-Java library version using an R option before loading the package:

options(loadeR.java_forced_version = "5.9.0")
library(loadeR.java)