106 Stars
Updated Last
12 Months Ago
Started In
November 2013


master GHA CI v0.7 GHA CI Windows x86 CI Gitter

Call Java programs from Julia.


Documentation is available at http://juliainterop.github.io/JavaCall.jl

Quick Start Example Usage


julia> using Pkg; Pkg.activate(; temp = true)
  Activating new project at `/tmp/jl_e6uPja`

julia> using JavaCall
 │ Package JavaCall not found, but a package named JavaCall is available from a
 │ registry. 
 │ Install package?
 │   (jl_e6uPja) pkg> add JavaCall 
 └ (y/n) [y]: y


julia> JavaCall.addClassPath(pwd()) # Set appropriate classpath

julia> JavaCall.addOpts("-Xmx1024M") # Use 1 GB of memory
OrderedCollections.OrderedSet{String} with 1 element:

julia> JavaCall.addOpts("-Xrs") # Disable signal handling in the JVM, reducing performance but enhancing compatability
OrderedCollections.OrderedSet{String} with 2 elements:

julia> JavaCall.init() # Call before using `jcall` or `jfield`. Do not use this in package `__init__()` to allow other packages to add classpaths or options.

julia> jls = @jimport java.lang.System

julia> out = jfield(jls, "out", @jimport java.io.PrintStream) # Third arg is optional, but helps type stability.
JavaObject{Symbol("java.io.PrintStream")}(JavaCall.JavaLocalRef(Ptr{Nothing} @0x0000000003ecda38))

julia> jcall(out, "println", Nothing, (JString,), "Hello World")
Hello World


  • 0.7 branch is currently being maintained for bug fixes only
  • master branch is currently proposed to be v0.8.0

Julia version compatability

JavaCall should continue to work with Julia 1.0.x (formerly a long term support version of Julia).

JavaCall and its dependents do not work correctly on Julia 1.1 and Julia 1.2. On Julia 1.1 and 1.2, you may see segfaults or incorrect results. This is typically due to stack corruption.

For Julia pre-1.5, consider the RootTaskRepl.jl package. With RootTaskREPL.jl, JavaCall is able to execute fine without the need of JULIA_COPY_STACKS=1 with the exception of @async calls. Starting with the Julia 1.5, the REPL backend now runs on the root Task by default.

Julia 1.3.0 through Julia 1.6.2 are tested and guaranteed to work on Linux, macOS, and Windows via continuous integration. Julia 1.6.2 and newer should work on Linux and Windows. The JULIA_COPY_STACKS environment variable should be set to 1 on macOS and Linux, but not Windows.

Apple macOS

JavaCall works on Julia 1.0 and Julia 1.3 to Julia 1.6.2. Please set the environment variable JULIA_COPY_STACKS = 1.

As of Julia 1.6.3, JavaCall fails on macOS due to a fatal segmentation fault, signal (11). See JavaCall#151 and JuliaLang/julia#40056.

The current developers of JavaCall do not posess current Apple hardware to debug this issue. Help is needed.

Julia 1.0 and Julia 1.6.2 are tested via Github Actions continuous integration on macOS.

Windows Operating System

Do not set the environmental variable JULIA_COPY_STACKS or set the variable to 0.

To use jcall with @async, start Julia in the following way:

$ julia -i -e "using JavaCall; JavaCall.init()"

Windows currently lacks support for multithreaded access to the JVM.

Julia 1.0, 1.6, 1 (latest release), and nightly are tested on Windows via Github Actions continuous integration. x86 compatability is also tested on the latest Julia 1 release.


On Julia 1.3 and newer, please set the environment variable JULIA_COPY_STACKS = 1.

Multithreaded access to the JVM is supported as JavaCall version 0.8.0.

Julia 1.0, 1.6, 1 (latest release), and nightly are tested on Linux via Github Actions continuous integration.

Other Operating Systems

JavaCall has not been tested on operating systems other than macOS, Windows, or Linux. You should probably set the environment variable JULIA_COPY_STACKS = 1. If you have success using JavaCall on another operating system than listed above, please create an issue or pull request to let us know about compatability.