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Discover system-wide Java installations

Source: R/java_find.R
java_find_system.Rd

Scans the system for installed Java Development Kits (JDKs). Implementation based on CMake FindJava.cmake logic, rJava detection, and standard OS checks.

Note: This function only returns true system installations. Java installations managed by rJavaEnv (stored in the package cache) are explicitly excluded, even if JAVA_HOME or PATH currently point to them.

Usage

java_find_system(quiet = TRUE, .use_cache = FALSE)

Arguments

quiet

Logical. If TRUE, suppresses informational messages.

.use_cache

Logical. If TRUE, uses memoisation cache for the expensive system scanning part. The is_default flag is always calculated dynamically based on the current JAVA_HOME. Default: FALSE (bypass cache for safety). Set to TRUE for performance in loops or repeated calls.

Value

A data frame with columns:

  • java_home: Character. Path to the Java home directory.

  • version: Character. Major Java version (e.g., "17", "21").

  • is_default: Logical. TRUE if this matches the current system default Java (determined by JAVA_HOME or PATH). Rows are ordered with the default Java first (if detected), then by version descending. Returns an empty data frame if no Java installations are found.

Performance

The system scan is memoised (cached) for the session duration. First scan: ~209ms. Subsequent scans with .use_cache = TRUE: <1ms. The is_default flag is always calculated fresh to reflect current JAVA_HOME.

Examples

# \donttest{
# List all system Java installations
java_find_system()
#>                            java_home version is_default
#> 1   /usr/lib/jvm/temurin-8-jdk-amd64       8      FALSE
#> 2  /usr/lib/jvm/temurin-11-jdk-amd64      11      FALSE
#> 3  /usr/lib/jvm/temurin-17-jdk-amd64      17      FALSE
#> 4 /usr/lib/jvm/java-21-openjdk-amd64      21      FALSE
#> 5  /usr/lib/jvm/temurin-21-jdk-amd64      21      FALSE
#> 6  /usr/lib/jvm/temurin-25-jdk-amd64      25      FALSE

# Use cache for faster repeated calls if you are using it in your R package
java_find_system(.use_cache = TRUE)
#>                            java_home version is_default
#> 1   /usr/lib/jvm/temurin-8-jdk-amd64       8      FALSE
#> 2  /usr/lib/jvm/temurin-11-jdk-amd64      11      FALSE
#> 3  /usr/lib/jvm/temurin-17-jdk-amd64      17      FALSE
#> 4 /usr/lib/jvm/java-21-openjdk-amd64      21      FALSE
#> 5  /usr/lib/jvm/temurin-21-jdk-amd64      21      FALSE
#> 6  /usr/lib/jvm/temurin-25-jdk-amd64      25      FALSE
# }