CloudSlang/score

Shared coding conventions allow teams to collaborate efficiently. This rule checks that all constant names match a provided regular expression.

Noncompliant Code Example

With the default regular expression ^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$:

public class MyClass {
  public static final int first = 1;
}

public enum MyEnum {
  first;
}

Compliant Solution

public class MyClass {
  public static final int FIRST = 1;
}

public enum MyEnum {
  FIRST;
}

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.

There are several reasons for a method not to have a method body:

• It is an unintentional omission, and should be fixed to prevent an unexpected behavior in production.
• It is not yet, or never will be, supported. In this case an UnsupportedOperationException should be thrown.
• The method is an intentionally-blank override. In this case a nested comment should explain the reason for the blank override.

Noncompliant Code Example

public void doSomething() {
}

public void doSomethingElse() {
}

Compliant Solution

@Override
public void doSomething() {
  // Do nothing because of X and Y.
}

@Override
public void doSomethingElse() {
  throw new UnsupportedOperationException();
}

Exceptions

Default (no-argument) constructors are ignored when there are other constructors in the class, as are empty methods in abstract classes.

public abstract class Animal {
  void speak() {  // default implementation ignored
  }
}

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.

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.

Non-encoded control characters and whitespace characters are often injected in the source code because of a bad manipulation. They are either invisible or difficult to recognize, which can result in bugs when the string is not what the developer expects. If you actually need to use a control character use their encoded version (ex: ASCII \n,\t,... or Unicode U+000D, U+0009,...).

This rule raises an issue when the following characters are seen in a literal string:

• ASCII control character. (character index < 32 or = 127)
• Unicode whitespace characters.
• Unicode C0 control characters
• Unicode characters U+200B, U+200C, U+200D, U+2060, U+FEFF, U+2028, U+2029

No issue will be raised on the simple space character. Unicode U+0020, ASCII 32.

Noncompliant Code Example

String tabInside = "A   B";  // Noncompliant, contains a tabulation
String zeroWidthSpaceInside = "foo​bar"; // Noncompliant, it contains a U+200B character inside
char tab = '    ';

Compliant Solution

String tabInside = "A\tB";  // Compliant, uses escaped value
String zeroWidthSpaceInside = "foo\u200Bbar";  // Compliant, uses escaped value
char tab = '\t';

Exceptions

Text Blocks string literals (java 13 three double-quote marks) can contain tabulations to allow indentation using tabulations.

Non-encoded control characters and whitespace characters are often injected in the source code because of a bad manipulation. They are either invisible or difficult to recognize, which can result in bugs when the string is not what the developer expects. If you actually need to use a control character use their encoded version (ex: ASCII \n,\t,... or Unicode U+000D, U+0009,...).

This rule raises an issue when the following characters are seen in a literal string:

• ASCII control character. (character index < 32 or = 127)
• Unicode whitespace characters.
• Unicode C0 control characters
• Unicode characters U+200B, U+200C, U+200D, U+2060, U+FEFF, U+2028, U+2029

No issue will be raised on the simple space character. Unicode U+0020, ASCII 32.

Noncompliant Code Example

String tabInside = "A   B";  // Noncompliant, contains a tabulation
String zeroWidthSpaceInside = "foo​bar"; // Noncompliant, it contains a U+200B character inside
char tab = '    ';

Compliant Solution

String tabInside = "A\tB";  // Compliant, uses escaped value
String zeroWidthSpaceInside = "foo\u200Bbar";  // Compliant, uses escaped value
char tab = '\t';

Exceptions

Text Blocks string literals (java 13 three double-quote marks) can contain tabulations to allow indentation using tabulations.

Many consider clone and Cloneable broken in Java, largely because the rules for overriding clone are tricky and difficult to get right, according to Joshua Bloch:

Object's clone method is very tricky. It's based on field copies, and it's "extra-linguistic." It creates an object without calling a constructor. There are no guarantees that it preserves the invariants established by the constructors. There have been lots of bugs over the years, both in and outside Sun, stemming from the fact that if you just call super.clone repeatedly up the chain until you have cloned an object, you have a shallow copy of the object. The clone generally shares state with the object being cloned. If that state is mutable, you don't have two independent objects. If you modify one, the other changes as well. And all of a sudden, you get random behavior.

A copy constructor or copy factory should be used instead.

This rule raises an issue when clone is overridden, whether or not Cloneable is implemented.

Noncompliant Code Example

public class MyClass {
  // ...

  public Object clone() { // Noncompliant
    //...
  }
}

Compliant Solution

public class MyClass {
  // ...

  MyClass (MyClass source) {
    //...
  }
}

See

• Copy Constructor versus Cloning

See Also

• {rule:java:S2157} - "Cloneables" should implement "clone"
• {rule:java:S1182} - Classes that override "clone" should be "Cloneable" and call "super.clone()"

Shared coding conventions allow teams to collaborate efficiently. This rule checks that all constant names match a provided regular expression.

Noncompliant Code Example

With the default regular expression ^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$:

public class MyClass {
  public static final int first = 1;
}

public enum MyEnum {
  first;
}

Compliant Solution

public class MyClass {
  public static final int FIRST = 1;
}

public enum MyEnum {
  FIRST;
}

There are several reasons for a method not to have a method body:

• It is an unintentional omission, and should be fixed to prevent an unexpected behavior in production.
• It is not yet, or never will be, supported. In this case an UnsupportedOperationException should be thrown.
• The method is an intentionally-blank override. In this case a nested comment should explain the reason for the blank override.

Noncompliant Code Example

public void doSomething() {
}

public void doSomethingElse() {
}

Compliant Solution

@Override
public void doSomething() {
  // Do nothing because of X and Y.
}

@Override
public void doSomethingElse() {
  throw new UnsupportedOperationException();
}

Exceptions

Default (no-argument) constructors are ignored when there are other constructors in the class, as are empty methods in abstract classes.

public abstract class Animal {
  void speak() {  // default implementation ignored
  }
}

Java 7 introduced the try-with-resources statement, which guarantees that the resource in question will be closed. Since the new syntax is closer to bullet-proof, it should be preferred over the older try/catch/finally version.

This rule checks that close-able resources are opened in a try-with-resources statement.

Note that this rule is automatically disabled when the project's sonar.java.source is lower than 7.

Noncompliant Code Example

FileReader fr = null;
BufferedReader br = null;
try {
  fr = new FileReader(fileName);
  br = new BufferedReader(fr);
  return br.readLine();
} catch (...) {
} finally {
  if (br != null) {
    try {
      br.close();
    } catch(IOException e){...}
  }
  if (fr != null ) {
    try {
      br.close();
    } catch(IOException e){...}
  }
}

Compliant Solution

try (
    FileReader fr = new FileReader(fileName);
    BufferedReader br = new BufferedReader(fr)
  ) {
  return br.readLine();
}
catch (...) {}

or

try (BufferedReader br =
        new BufferedReader(new FileReader(fileName))) { // no need to name intermediate resources if you don't want to
  return br.readLine();
}
catch (...) {}

See

• CERT, ERR54-J. - Use a try-with-resources statement to safely handle closeable resources

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 underlying implementation of String::replaceAll calls the java.util.regex.Pattern.compile() method each time it is called even if the first argument is not a regular expression. This has a significant performance cost and therefore should be used with care.

When String::replaceAll is used, the first argument should be a real regular expression. If it’s not the case, String::replace does exactly the same thing as String::replaceAll without the performance drawback of the regex.

This rule raises an issue for each String::replaceAll used with a String as first parameter which doesn’t contains special regex character or pattern.

Noncompliant Code Example

String init = "Bob is a Bird... Bob is a Plane... Bob is Superman!";
String changed = init.replaceAll("Bob is", "It's"); // Noncompliant
changed = changed.replaceAll("\\.\\.\\.", ";"); // Noncompliant

Compliant Solution

String init = "Bob is a Bird... Bob is a Plane... Bob is Superman!";
String changed = init.replace("Bob is", "It's");
changed = changed.replace("...", ";");

Or, with a regex:

String init = "Bob is a Bird... Bob is a Plane... Bob is Superman!";
String changed = init.replaceAll("\\w*\\sis", "It's");
changed = changed.replaceAll("\\.{3}", ";");

See

• {rule:java:S4248} - Regex patterns should not be created needlessly

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.