问题:

I understand that you can set the Java library path with an option (-Djava.library.path=/path/to/libs) before executing the program, but is there a place on the system where Java looks if you don't set it manually?

回答1:

Its default value depends on the operating system:

On Windows, it maps to PATH
On Linux, it maps to LD_LIBRARY_PATH
On OS X, it maps to DYLD_LIBRARY_PATH

回答2:

However, Matt Ball is not totally correct.

On my Linux box, my Java library path is

/usr/lib64/icedtea6/jre/lib/amd64/server:/usr/lib64/icedtea6/jre/lib/amd6ib/amd64:/usr/lib64:/lib64:/lib:/usr/lib

While my LD_LIBRARY_PATH is /usr/local/lib64.

回答3:

For Java 8, this differs based on OS. This is the behavior I observed:

Windows 10/Oracle JDK 8: java.library.path=%PATH%;.
macOS El Capitan/Oracle JDK 8: java.library.path=$JAVA_LIBRARY_PATH:~/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.. DYLD_LIBRARY_PATH and LD_LIBRARY_PATH variables are ignored. Moreover, both these variables are removed from the environment of Java applications.
Linux CentOS 7/Open JDK 8: java.library.path=$LD_LIBRARY_PATH:/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib