SONARJAVA-5630 Check that iterator contains a next element before calling next (#5199)

Author: romainbrenguier

java-checks/src/main/java/org/sonar/java/checks/RedundantJumpCheck.java

@@ -18,6 +18,7 @@
 
 import java.util.Arrays;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
 import org.sonar.check.Rule;
@@ -58,8 +59,8 @@ private void checkBlock(Block block) {
       && !isSwitchCaseChild(terminator)) {
 
       successorWithoutJump = nonEmptySuccessor(successorWithoutJump);
-      Block successor = nonEmptySuccessor(block.successors().iterator().next());
-      if (successorWithoutJump.equals(successor)) {
+      Iterator<Block> successors = block.successors().iterator();
+      if (successors.hasNext() && nonEmptySuccessor(successors.next()).equals(successorWithoutJump)) {
         reportIssue(terminator, "Remove this redundant jump.");
       }
     }

java-checks/src/test/files/checks/RedundantJumpCheck.java

@@ -120,4 +120,11 @@ public void throwing_exception() {
 
   public abstract void abstract_method();
 
+  void undefinedLabel(int values[]) {
+    for (int v: values) {
+      if (v == 2) {
+        continue label; // this should be a compiler error, but we want to test that the check does not crash
+      }
+    }
+  }
 }