multiple_contexts.java

Context c1 = Context.create("js");
Context c2 = Context.create("js");
String jsCode = "(function(x,y) { return JSON.stringify({x:x,y:y}); })";

Value json1 = c1.eval("js", jsCode);
Value json2 = c2.eval("js", jsCode);

Thread thread = new Thread(new Runnable() {
  @Override
  public void run() {
    while (true) {
      json1.execute(42,43).asString();
    }
  }
});
thread.start();

while (true) {
  json2.execute(44,45).asString();
}