diff --git a/src/main/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructure.java b/src/main/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructure.java
index 1ab06ab..944cc42 100644
--- a/src/main/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructure.java
+++ b/src/main/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructure.java
@@ -9,7 +9,17 @@
 
 import java.io.IOException;
 import java.io.Serializable;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Queue;
+import java.util.Stack;
 
 @JsonSerialize(using = AccessStructure.Serialize.class)
 @JsonDeserialize(using = AccessStructure.Deserialize.class)
diff --git a/src/test/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructureTest.java b/src/test/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructureTest.java
index bedfc0f..3a135fb 100644
--- a/src/test/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructureTest.java
+++ b/src/test/java/sg/edu/ntu/sce/sands/crypto/dcpabe/ac/AccessStructureTest.java
@@ -1,6 +1,5 @@
 package sg.edu.ntu.sce.sands.crypto.dcpabe.ac;
 
-import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import sg.edu.ntu.sce.sands.crypto.dcpabe.ac.AccessStructure.MatrixElement;
 
@@ -9,17 +8,12 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class AccessStructureTest {
-    private AccessStructure arho;
-    private String policy;
-
-    @BeforeEach
-    public void setUp() {
-        policy = "and or D and C B A";
-        arho = AccessStructure.buildFromPolicy(policy);
-    }
+    private final String policy = "and or D and C B A";
 
     @Test
     public void testPolicyToStringConversion() throws Exception {
+        AccessStructure arho = AccessStructure.buildFromPolicy(policy);
+
         String recoveredPolicy = arho.toString();
         assertEquals(policy, recoveredPolicy);
     }