5 files changed, 17 insertions, 9 deletions
diff --git a/sonar-duplications/src/main/java/org/sonar/duplications/detector/suffixtree/TextSet.java b/sonar-duplications/src/main/java/org/sonar/duplications/detector/suffixtree/TextSet.java
index 51ecbe54294..e92398b26f5 100644
--- a/sonar-duplications/src/main/java/org/sonar/duplications/detector/suffixtree/TextSet.java
+++ b/sonar-duplications/src/main/java/org/sonar/duplications/detector/suffixtree/TextSet.java
@@ -91,7 +91,7 @@ public final class TextSet extends AbstractText {
 
     @Override
     public boolean equals(Object obj) {
-      return (this.getClass() == obj.getClass()) && (((Terminator) obj).stringNumber == stringNumber);
+      return obj != null && this.getClass() == obj.getClass() && (((Terminator) obj).stringNumber == stringNumber);
     }
 
     @Override
diff --git a/sonar-duplications/src/main/java/org/sonar/duplications/index/CloneGroup.java b/sonar-duplications/src/main/java/org/sonar/duplications/index/CloneGroup.java
index b840c2f55f0..818e018d4bb 100644
--- a/sonar-duplications/src/main/java/org/sonar/duplications/index/CloneGroup.java
+++ b/sonar-duplications/src/main/java/org/sonar/duplications/index/CloneGroup.java
@@ -23,6 +23,8 @@ import com.google.common.annotations.Beta;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 
+import javax.annotation.Nullable;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -134,8 +136,8 @@ public class CloneGroup {
    * Two groups are equal, if they have same length, same origins and contain same parts in same order.
    */
   @Override
-  public boolean equals(Object object) {
-    if (this.getClass() != object.getClass()) {
+  public boolean equals(@Nullable Object object) {
+    if (object == null || this.getClass() != object.getClass()) {
       return false;
     }
     CloneGroup another = (CloneGroup) object;
diff --git a/sonar-duplications/src/main/java/org/sonar/duplications/index/ClonePart.java b/sonar-duplications/src/main/java/org/sonar/duplications/index/ClonePart.java
index 630f52c1350..0130f167197 100644
--- a/sonar-duplications/src/main/java/org/sonar/duplications/index/ClonePart.java
+++ b/sonar-duplications/src/main/java/org/sonar/duplications/index/ClonePart.java
@@ -21,6 +21,8 @@ package org.sonar.duplications.index;
 
 import org.sonar.duplications.CodeFragment;
 
+import javax.annotation.Nullable;
+
 public class ClonePart implements CodeFragment {
 
   private final String resourceId;
@@ -63,8 +65,8 @@ public class ClonePart implements CodeFragment {
   }
 
   @Override
-  public boolean equals(Object obj) {
-    if (this.getClass() == obj.getClass()) {
+  public boolean equals(@Nullable Object obj) {
+    if (obj != null && this.getClass() == obj.getClass()) {
       ClonePart another = (ClonePart) obj;
       return another.resourceId.equals(resourceId)
         && another.startLine == startLine
diff --git a/sonar-duplications/src/main/java/org/sonar/duplications/statement/Statement.java b/sonar-duplications/src/main/java/org/sonar/duplications/statement/Statement.java
index dc1c8ac402d..f698e61805b 100644
--- a/sonar-duplications/src/main/java/org/sonar/duplications/statement/Statement.java
+++ b/sonar-duplications/src/main/java/org/sonar/duplications/statement/Statement.java
@@ -22,6 +22,8 @@ package org.sonar.duplications.statement;
 import org.sonar.duplications.CodeFragment;
 import org.sonar.duplications.token.Token;
 
+import javax.annotation.Nullable;
+
 import java.util.List;
 
 public class Statement implements CodeFragment {
@@ -81,8 +83,8 @@ public class Statement implements CodeFragment {
   }
 
   @Override
-  public boolean equals(Object obj) {
-    if (this.getClass() != obj.getClass()) {
+  public boolean equals(@Nullable Object obj) {
+    if (obj ==  null || this.getClass() != obj.getClass()) {
       return false;
     }
     Statement other = (Statement) obj;
diff --git a/sonar-duplications/src/main/java/org/sonar/duplications/token/Token.java b/sonar-duplications/src/main/java/org/sonar/duplications/token/Token.java
index c1c374e7f52..e738ebc404e 100644
--- a/sonar-duplications/src/main/java/org/sonar/duplications/token/Token.java
+++ b/sonar-duplications/src/main/java/org/sonar/duplications/token/Token.java
@@ -19,6 +19,8 @@
  */
 package org.sonar.duplications.token;
 
+import javax.annotation.Nullable;
+
 public class Token {
 
   private final int line;
@@ -49,8 +51,8 @@ public class Token {
   }
 
   @Override
-  public boolean equals(Object object) {
-    if (this.getClass() == object.getClass()) {
+  public boolean equals(@Nullable Object object) {
+    if (object != null && this.getClass() == object.getClass()) {
       Token anotherToken = (Token) object;
       return anotherToken.line == line && anotherToken.column == column && anotherToken.value.equals(value);
     }