Adobe-Consulting-Services/acs-aem-commons

Conditional expressions which are always true or false can lead to dead code. Such code is always buggy and should never be used in production.

Noncompliant Code Example

a = false;
if (a) { // Noncompliant
  doSomething(); // never executed
}

if (!a || b) { // Noncompliant; "!a" is always "true", "b" is never evaluated
  doSomething();
} else {
  doSomethingElse(); // never executed
}

Exceptions

This rule will not raise an issue in either of these cases:

• When the condition is a single final boolean

final boolean debug = false;
//...
if (debug) {
  // Print something
}

• When the condition is literally true or false.

if (true) {
  // do something
}

In these cases it is obvious the code is as intended.

See

• MITRE, CWE-570 - Expression is Always False
• MITRE, CWE-571 - Expression is Always True
• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

Using such generic exceptions as Error, RuntimeException, Throwable, and Exception prevents calling methods from handling true, system-generated exceptions differently than application-generated errors.

Noncompliant Code Example

public void foo(String bar) throws Throwable {  // Noncompliant
  throw new RuntimeException("My Message");     // Noncompliant
}

Compliant Solution

public void foo(String bar) {
  throw new MyOwnRuntimeException("My Message");
}

Exceptions

Generic exceptions in the signatures of overriding methods are ignored, because overriding method has to follow signature of the throw declaration in the superclass. The issue will be raised on superclass declaration of the method (or won't be raised at all if superclass is not part of the analysis).

@Override
public void myMethod() throws Exception {...}

Generic exceptions are also ignored in the signatures of methods that make calls to methods that throw generic exceptions.

public void myOtherMethod throws Exception {
  doTheThing();  // this method throws Exception
}

See

• MITRE, CWE-397 - Declaration of Throws for Generic Exception
• CERT, ERR07-J. - Do not throw RuntimeException, Exception, or Throwable

Generic types shouldn't be used raw (without type parameters) in variable declarations or return values. Doing so bypasses generic type checking, and defers the catch of unsafe code to runtime.

Noncompliant Code Example

List myList; // Noncompliant
Set mySet; // Noncompliant

Compliant Solution

List<String> myList;
Set<? extends Number> mySet;

A reference to null should never be dereferenced/accessed. Doing so will cause a NullPointerException to be thrown. At best, such an exception will cause abrupt program termination. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures.

Note that when they are present, this rule takes advantage of @CheckForNull and @Nonnull annotations defined in JSR-305 to understand which values are and are not nullable except when @Nonnull is used on the parameter to equals, which by contract should always work with null.

Noncompliant Code Example

@CheckForNull
String getName(){...}

public boolean isNameEmpty() {
  return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked
}

Connection conn = null;
Statement stmt = null;
try{
  conn = DriverManager.getConnection(DB_URL,USER,PASS);
  stmt = conn.createStatement();
  // ...

}catch(Exception e){
  e.printStackTrace();
}finally{
  stmt.close();   // Noncompliant; stmt could be null if an exception was thrown in the try{} block
  conn.close();  // Noncompliant; conn could be null if an exception was thrown
}

private void merge(@Nonnull Color firstColor, @Nonnull Color secondColor){...}

public  void append(@CheckForNull Color color) {
    merge(currentColor, color);  // Noncompliant; color should be null-checked because merge(...) doesn't accept nullable parameters
}

void paint(Color color) {
  if(color == null) {
    System.out.println("Unable to apply color " + color.toString());  // Noncompliant; NullPointerException will be thrown
    return;
  }
  ...
}

See

• MITRE, CWE-476 - NULL Pointer Dereference
• CERT, EXP34-C. - Do not dereference null pointers
• CERT, EXP01-J. - Do not use a null in a case where an object is required

Unused parameters are misleading. Whatever the values passed to such parameters, the behavior will be the same.

Noncompliant Code Example

void doSomething(int a, int b) {     // "b" is unused
  compute(a);
}

Compliant Solution

void doSomething(int a) {
  compute(a);
}

Exceptions

The rule will not raise issues for unused parameters:

• that are annotated with @javax.enterprise.event.Observes
• in overrides and implementation methods
• in interface default methods
• in non-private methods that only throw or that have empty bodies
• in annotated methods, unless the annotation is @SuppressWarning("unchecked") or @SuppressWarning("rawtypes"), in which case the annotation will be ignored
• in overridable methods (non-final, or not member of a final class, non-static, non-private), if the parameter is documented with a proper javadoc.

@Override
void doSomething(int a, int b) {     // no issue reported on b
  compute(a);
}

public void foo(String s) {
  // designed to be extended but noop in standard case
}

protected void bar(String s) {
  //open-closed principle
}

public void qix(String s) {
  throw new UnsupportedOperationException("This method should be implemented in subclasses");
}

/**
 * @param s This string may be use for further computation in overriding classes
 */
protected void foobar(int a, String s) { // no issue, method is overridable and unused parameter has proper javadoc
  compute(a);
}

See

• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

Generic types shouldn't be used raw (without type parameters) in variable declarations or return values. Doing so bypasses generic type checking, and defers the catch of unsafe code to runtime.

Noncompliant Code Example

List myList; // Noncompliant
Set mySet; // Noncompliant

Compliant Solution

List<String> myList;
Set<? extends Number> mySet;

Abstract classes should not have public constructors. Constructors of abstract classes can only be called in constructors of their subclasses. So there is no point in making them public. The protected modifier should be enough.

Noncompliant Code Example

public abstract class AbstractClass1 {
    public AbstractClass1 () { // Noncompliant, has public modifier
        // do something here
    }
}

Compliant Solution

public abstract class AbstractClass2 {
    protected AbstractClass2 () {
        // do something here
    }
}

Generic types shouldn't be used raw (without type parameters) in variable declarations or return values. Doing so bypasses generic type checking, and defers the catch of unsafe code to runtime.

Noncompliant Code Example

List myList; // Noncompliant
Set mySet; // Noncompliant

Compliant Solution

List<String> myList;
Set<? extends Number> mySet;

Conditional expressions which are always true or false can lead to dead code. Such code is always buggy and should never be used in production.

Noncompliant Code Example

a = false;
if (a) { // Noncompliant
  doSomething(); // never executed
}

if (!a || b) { // Noncompliant; "!a" is always "true", "b" is never evaluated
  doSomething();
} else {
  doSomethingElse(); // never executed
}

Exceptions

This rule will not raise an issue in either of these cases:

• When the condition is a single final boolean

final boolean debug = false;
//...
if (debug) {
  // Print something
}

• When the condition is literally true or false.

if (true) {
  // do something
}

In these cases it is obvious the code is as intended.

See

• MITRE, CWE-570 - Expression is Always False
• MITRE, CWE-571 - Expression is Always True
• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

Early classes of the Java API, such as Vector, Hashtable and StringBuffer, were synchronized to make them thread-safe. Unfortunately, synchronization has a big negative impact on performance, even when using these collections from a single thread.

It is better to use their new unsynchronized replacements:

• ArrayList or LinkedList instead of Vector
• Deque instead of Stack
• HashMap instead of Hashtable
• StringBuilder instead of StringBuffer

Even when used in synchronized context, you should think twice before using it, since it's usage can be tricky. If you are confident the usage is legitimate, you can safely ignore this warning.

Noncompliant Code Example

Vector cats = new Vector();

Compliant Solution

ArrayList cats = new ArrayList();

Exceptions

Use of those synchronized classes is ignored in the signatures of overriding methods.

@Override
public Vector getCats() {...}

Unused parameters are misleading. Whatever the values passed to such parameters, the behavior will be the same.

Noncompliant Code Example

void doSomething(int a, int b) {     // "b" is unused
  compute(a);
}

Compliant Solution

void doSomething(int a) {
  compute(a);
}

Exceptions

The rule will not raise issues for unused parameters:

• that are annotated with @javax.enterprise.event.Observes
• in overrides and implementation methods
• in interface default methods
• in non-private methods that only throw or that have empty bodies
• in annotated methods, unless the annotation is @SuppressWarning("unchecked") or @SuppressWarning("rawtypes"), in which case the annotation will be ignored
• in overridable methods (non-final, or not member of a final class, non-static, non-private), if the parameter is documented with a proper javadoc.

@Override
void doSomething(int a, int b) {     // no issue reported on b
  compute(a);
}

public void foo(String s) {
  // designed to be extended but noop in standard case
}

protected void bar(String s) {
  //open-closed principle
}

public void qix(String s) {
  throw new UnsupportedOperationException("This method should be implemented in subclasses");
}

/**
 * @param s This string may be use for further computation in overriding classes
 */
protected void foobar(int a, String s) { // no issue, method is overridable and unused parameter has proper javadoc
  compute(a);
}

See

• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed