1. SonarQube code scan error analysis: String literals should not be duplicated

Recently, I started to use code scanning-related tools to evaluate the quality of the code developed and scanned many problems. In order to improve my ability, it is necessary to study the details of these rules. This column is specially opened. One is the study summary and the other is the record. The growth process empowers the vast number of bloggers, I hope everyone likes it

String literals should not be duplicated

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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.

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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
}

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Compliant Solution

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

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

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Exceptions

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