java: add ThreadSafe query (P3)

Co-authored-by: Raúl Pardo <raul.pardo@protonmail.com>
Co-authored-by: SimonJorgensenMancofi <simon.jorgensen@mancofi.dk>
Co-authored-by: Bjørnar Haugstad Jåtten <bjornjaat@hotmail.com>

java/ql/test/query-tests/ThreadSafe/examples/Test2.java

@@ -0,0 +1,22 @@
+package examples;
+
+import java.util.ArrayList;
+
+// Note: Not marked as thread-safe
+// We inherit from this in Test3Super.java
+public class Test2 {
+  int x;
+  protected ArrayList<String> lst = new ArrayList<>();
+
+  public Test2() {
+    this.x = 0;
+  }
+
+  public void changeX() {
+    this.x = x + 1;
+  }
+
+  public void changeLst() {
+    lst.add("Hello");
+  }
+}