Page History

A switch statement is comprised of block comprises several case labels , and a an optional but highly recommended default label. The default label is not required, but strongly recommended. The statements following a case label conventionally By convention, statements that follow each case label end with a break; statement, which moves control flow responsible for transferring the control to the end of the switch block. If When omitted, control flow falls through to the next case statement in the switch blocksubsequent case label gets executed. Because the break statement is not required, omitting it optional, its omission produces no compiler warnings, and if this was . If this behavior is unintentional, it can lead to an unexpected undesirable control flowflows.

Noncompliant Code Example

In this noncompliant code example, the case where wherein the card = is 11 does not have a break statement. Thus, the statements for card = 12 are also executed when card = 11.

int card = 11;

switch (card) {
  /* ... */
  case 11: 
    System.out.println("Jack");
  case 12: 
    System.out.println("Queen"); 
    break;
  case 13: 
    System.out.println("King"); 
    break;
  default: 
    System.out.println("Invalid Card"); 
  break;
}

Compliant Solution

In the this compliant solution, each case label is ended with (including the default) is terminated by a break statement.

int card = 11;

switch (card) {
  /* ... */
  case 11: 
    System.out.println("Jack");
    break;
  case 12: 
    System.out.println("Queen"); 
    break;
  case 13: 
    System.out.println("King"); 
    break;
  default: 
    System.out.println("Invalid Card"); 
    break;
}

Exceptions

EX1: The last label in a switch statement requires no break. The break statement serves to skip to the end of the switch block, so control flow will continue to statements following the switch block with or without it. . Conventionally, the last label is the default label.

EX2: In some cases, where control flow is intended to execute the same code for multiple cases, it is permissible to omit the break statement. However, these instances must be explicitly documented.

int card=11;
int value;

/* Case 11,12,13 fall through to the same case */
switch (card) {
  /* MSC13-J:EX2: these three cases are treated identically  */
  case 11: 
  case 12: 
  case 13: 
    value=10; 
  break;
  default: 
    /* Handle Error Condition */ 
}

EX3: A case block needs no break statement if its last statement is a return or throw.

Risk Assessment

...

Other Languages

This rule appears in the C Secure Coding Standard as MSC17-C. Finish every set of statements associated with a case label with a break statement.

...