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/Test.java

@@ -0,0 +1,76 @@
+package examples;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+@ThreadSafe
+public class Test {
+  /**
+   * Escaping field due to public visuability.
+   */
+  int publicField;
+  
+  private int y;
+  final int immutableField = 1;
+
+  // As of the below examples with synchronized as well. Except the incorretly placed lock.
+
+  private Lock lock = new ReentrantLock();
+
+  /**
+   * Calls the a method where y field escapes.
+   * @param y
+   */
+  public void setYAgainInCorrect(int t) {
+    setYPrivate(t);
+  }
+
+  /**
+   * Locks the method where y field escapes.
+   * @param y
+   */
+  public void setYAgainCorrect(int y) {
+    lock.lock();
+    setYPrivate(y);
+    lock.unlock();
+  }
+
+  /**
+   * No escaping y field. Locks the y before assignment.
+   * @param y
+   */
+  public void setYCorrect(int y) {
+    lock.lock();
+    this.y = y; // $ Alert
+    lock.unlock();
+  }
+
+  /**
+   * No direct escaping, since it method is private. Only escaping if another public method uses this.
+   * @param y
+   */
+  private void setYPrivate(int y) {
+    this.y = y;
+  }
+
+  /**
+   * Incorretly locks y.
+   * @param y
+   */
+  public void setYWrongLock(int y) {
+    this.y = y;
+    lock.lock();
+    lock.unlock();
+  }
+
+  public synchronized int getImmutableField() {
+    return immutableField;
+  }
+
+  public synchronized int getImmutableField2() {
+    return immutableField;
+  }
+
+  public void testMethod() {
+    this.y = y + 2;
+  }
+}