hyperrail/hyperrail-for-android

A dead store happens when a local variable is assigned a value that is not read by any subsequent instruction. Calculating or retrieving a value only to then overwrite it or throw it away, could indicate a serious error in the code. Even if it's not an error, it is at best a waste of resources. Therefore all calculated values should be used.

Noncompliant Code Example

i = a + b; // Noncompliant; calculation result not used before value is overwritten
i = compute();

Compliant Solution

i = a + b;
i += compute();

Exceptions

This rule ignores initializations to -1, 0, 1, null, true, false and "".

See

• MITRE, CWE-563 - Assignment to Variable without Use ('Unused Variable')
• CERT, MSC13-C. - Detect and remove unused values
• CERT, MSC56-J. - Detect and remove superfluous code and values

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

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

The requirement for a final default clause is defensive programming. The clause should either take appropriate action, or contain a suitable comment as to why no action is taken.

Noncompliant Code Example

switch (param) {  //missing default clause
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

switch (param) {
  default: // default clause should be the last one
    error();
    break;
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

Compliant Solution

switch (param) {
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
  default:
    error();
    break;
}

Exceptions

If the switch parameter is an Enum and if all the constants of this enum are used in the case statements, then no default clause is expected.

Example:

public enum Day {
    SUNDAY, MONDAY
}
...
switch(day) {
  case SUNDAY:
    doSomething();
    break;
  case MONDAY:
    doSomethingElse();
    break;
}

See

• MITRE, CWE-478 - Missing Default Case in Switch Statement
• CERT, MSC01-C. - Strive for logical completeness

The requirement for a final default clause is defensive programming. The clause should either take appropriate action, or contain a suitable comment as to why no action is taken.

Noncompliant Code Example

switch (param) {  //missing default clause
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

switch (param) {
  default: // default clause should be the last one
    error();
    break;
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

Compliant Solution

switch (param) {
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
  default:
    error();
    break;
}

Exceptions

If the switch parameter is an Enum and if all the constants of this enum are used in the case statements, then no default clause is expected.

Example:

public enum Day {
    SUNDAY, MONDAY
}
...
switch(day) {
  case SUNDAY:
    doSomething();
    break;
  case MONDAY:
    doSomethingElse();
    break;
}

See

• MITRE, CWE-478 - Missing Default Case in Switch Statement
• CERT, MSC01-C. - Strive for logical completeness

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Utility classes, which are collections of static members, are not meant to be instantiated. Even abstract utility classes, which can be extended, should not have public constructors.

Java adds an implicit public constructor to every class which does not define at least one explicitly. Hence, at least one non-public constructor should be defined.

Noncompliant Code Example

class StringUtils { // Noncompliant

  public static String concatenate(String s1, String s2) {
    return s1 + s2;
  }

}

Compliant Solution

class StringUtils { // Compliant

  private StringUtils() {
    throw new IllegalStateException("Utility class");
  }

  public static String concatenate(String s1, String s2) {
    return s1 + s2;
  }

}

Exceptions

When class contains public static void main(String[] args) method it is not considered as utility class and will be ignored by this rule.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

The requirement for a final default clause is defensive programming. The clause should either take appropriate action, or contain a suitable comment as to why no action is taken.

Noncompliant Code Example

switch (param) {  //missing default clause
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

switch (param) {
  default: // default clause should be the last one
    error();
    break;
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

Compliant Solution

switch (param) {
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
  default:
    error();
    break;
}

Exceptions

If the switch parameter is an Enum and if all the constants of this enum are used in the case statements, then no default clause is expected.

Example:

public enum Day {
    SUNDAY, MONDAY
}
...
switch(day) {
  case SUNDAY:
    doSomething();
    break;
  case MONDAY:
    doSomethingElse();
    break;
}

See

• MITRE, CWE-478 - Missing Default Case in Switch Statement
• CERT, MSC01-C. - Strive for logical completeness

The requirement for a final default clause is defensive programming. The clause should either take appropriate action, or contain a suitable comment as to why no action is taken.

Noncompliant Code Example

switch (param) {  //missing default clause
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

switch (param) {
  default: // default clause should be the last one
    error();
    break;
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
}

Compliant Solution

switch (param) {
  case 0:
    doSomething();
    break;
  case 1:
    doSomethingElse();
    break;
  default:
    error();
    break;
}

Exceptions

If the switch parameter is an Enum and if all the constants of this enum are used in the case statements, then no default clause is expected.

Example:

public enum Day {
    SUNDAY, MONDAY
}
...
switch(day) {
  case SUNDAY:
    doSomething();
    break;
  case MONDAY:
    doSomethingElse();
    break;
}

See

• MITRE, CWE-478 - Missing Default Case in Switch Statement
• CERT, MSC01-C. - Strive for logical completeness

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

The use of parentheses, even those not required to enforce a desired order of operations, can clarify the intent behind a piece of code. But redundant pairs of parentheses could be misleading, and should be removed.

Noncompliant Code Example

int x = (y / 2 + 1);   //Compliant even if the parenthesis are ignored by the compiler

if (a && ((x+y > 0))) {  // Noncompliant
  //...
}

return ((x + 1));  // Noncompliant

Compliant Solution

int x = (y / 2 + 1);

if (a && (x+y > 0)) {
  //...
}

return (x + 1);

Constructors for String, BigInteger, BigDecimal and the objects used to wrap primitives should never be used. Doing so is less clear and uses more memory than simply using the desired value in the case of strings, and using valueOf for everything else.

Noncompliant Code Example

String empty = new String(); // Noncompliant; yields essentially "", so just use that.
String nonempty = new String("Hello world"); // Noncompliant
Double myDouble = new Double(1.1); // Noncompliant; use valueOf
Integer integer = new Integer(1); // Noncompliant
Boolean bool = new Boolean(true); // Noncompliant
BigInteger bigInteger1 = new BigInteger("3"); // Noncompliant
BigInteger bigInteger2 = new BigInteger("9223372036854775807"); // Noncompliant
BigInteger bigInteger3 = new BigInteger("111222333444555666777888999"); // Compliant, greater than Long.MAX_VALUE

Compliant Solution

String empty = "";
String nonempty = "Hello world";
Double myDouble = Double.valueOf(1.1);
Integer integer = Integer.valueOf(1);
Boolean bool = Boolean.valueOf(true);
BigInteger bigInteger1 = BigInteger.valueOf(3);
BigInteger bigInteger2 = BigInteger.valueOf(9223372036854775807L);
BigInteger bigInteger3 = new BigInteger("111222333444555666777888999");

Exceptions

BigDecimal constructor with double argument is ignored as using valueOf instead might change resulting value. See {rule:java:S2111} .

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.

On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

Noncompliant Code Example

With the default threshold of 3:

public void run() {
  prepare("action1");                              // Noncompliant - "action1" is duplicated 3 times
  execute("action1");
  release("action1");
}

@SuppressWarning("all")                            // Compliant - annotations are excluded
private void method1() { /* ... */ }
@SuppressWarning("all")
private void method2() { /* ... */ }

public String method3(String a) {
  System.out.println("'" + a + "'");               // Compliant - literal "'" has less than 5 characters and is excluded
  return "";                                       // Compliant - literal "" has less than 5 characters and is excluded
}

Compliant Solution

private static final String ACTION_1 = "action1";  // Compliant

public void run() {
  prepare(ACTION_1);                               // Compliant
  execute(ACTION_1);
  release(ACTION_1);
}

Exceptions

To prevent generating some false-positives, literals having less than 5 characters are excluded.

If a private field is declared but not used in the program, it can be considered dead code and should therefore be removed. This will improve maintainability because developers will not wonder what the variable is used for.

Note that this rule does not take reflection into account, which means that issues will be raised on private fields that are only accessed using the reflection API.

Noncompliant Code Example

public class MyClass {
  private int foo = 42;

  public int compute(int a) {
    return a * 42;
  }

}

Compliant Solution

public class MyClass {
  public int compute(int a) {
    return a * 42;
  }
}

Exceptions

The Java serialization runtime associates with each serializable class a version number, called serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization.

A serializable class can declare its own serialVersionUID explicitly by declaring a field named serialVersionUID that must be static, final, and of type long. By definition those serialVersionUID fields should not be reported by this rule:

public class MyClass implements java.io.Serializable {
  private static final long serialVersionUID = 42L;
}

Moreover, this rule doesn't raise any issue on annotated fields.