Added new rule: "Avoid raising null pointer exceptions when a null check is possible

codeql-custom-queries-java/lang/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.expected

@@ -0,0 +1,3 @@
+| avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.java:6:11:6:40 | catch (...) | This catch-clause handles NullPointerException. Consider using null checks instead of relying on exception handling to avoid performance overhead. |
+| avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.java:14:11:14:40 | catch (...) | This catch-clause handles NullPointerException. Consider using null checks instead of relying on exception handling to avoid performance overhead. |
+| avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.java:22:11:22:74 | catch (...) | This catch-clause handles NullPointerException. Consider using null checks instead of relying on exception handling to avoid performance overhead. |

codeql-custom-queries-java/lang/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.java

@@ -0,0 +1,43 @@
+class nonCompliantNullCheck {
+    void nullCheckTest(String str) {
+        try {
+            String part = str.substring(5); // Noncompliant
+            System.out.println(part);
+        } catch (NullPointerException e) {
+            System.out.println("String is null");
+        }
+    }
+
+    void anotherNullCheckTest(Object obj) {
+        try {
+            obj.toString(); // Noncompliant
+        } catch (NullPointerException e) {
+            System.out.println("Object is null");
+        }
+    }
+
+    void multiCatchTest(String str) {
+        try {
+            int length = str.length(); // Noncompliant
+        } catch (NullPointerException | StringIndexOutOfBoundsException e) {
+            System.out.println("Error occurred");
+        }
+    }
+}
+
+class compliantNullCheck {
+    void nullCheckTest(String str) {
+        if (str != null && str.length() > 5) { // Compliant
+            String part = str.substring(5);
+            System.out.println(part);
+        } else {
+            System.out.println("String is null or too short");
+        }
+    }
+
+    void anotherNullCheckTest(Object obj) {
+        if (obj != null) { // Compliant
+            obj.toString();
+        }
+    }
+}

codeql-custom-queries-java/lang/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible.ql

@@ -0,0 +1,32 @@
+/**
+ * @name Avoid raising NullPointerExceptions when a null check is possible
+ * @description Identifies try-catch blocks that handle NullPointerException. Null checks should be performed to avoid NullPointerExceptions rather than relying on exception handling.
+ * @kind problem
+ * @problem.severity recommendation
+ * @precision high
+ * @id java/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible
+ * @tags java/lang/avoid-raising-null-pointer-exceptions-when-a-null-check-is-possible
+ */
+
+import java
+
+pragma[nomagic]
+predicate isNullPointerException(RefType rt) {
+  rt.hasQualifiedName("java.lang", "NullPointerException")
+}
+
+private RefType caughtType(TryStmt try, int index) {
+  exists(CatchClause cc | cc = try.getCatchClause(index) |
+    if cc.isMultiCatch()
+    then result = cc.getVariable().getTypeAccess().(UnionTypeAccess).getAnAlternative().getType()
+    else result = cc.getVariable().getType()
+  )
+}
+
+from TryStmt try, int index, RefType npeType
+where
+  try.getFile().isJavaSourceFile() and
+  npeType = caughtType(try, index) and
+  isNullPointerException(npeType)
+select try.getCatchClause(index),
+  "This catch-clause handles NullPointerException. Consider using null checks instead of relying on exception handling to avoid performance overhead."