An infinite loop with an empty body consumes CPU cycles but does nothing. Optimizing compilers and just-in-time systems (JITs) are permitted to (perhaps unexpectedly) remove such a loop. Consequently, programs must not include infinite loops with empty bodies.

Noncompliant Code Example

This noncompliant code example implements an idle task that continuously executes a loop without executing any instructions within the loop. An optimizing compiler or JIT could remove the while loop in this example.

public int nop() {
  while (true) {}
}

Compliant Solution (Thread.sleep())

This compliant solution avoids use of a meaningless infinite loop by invoking Thread.sleep() within the while loop. The loop body contains semantically meaningful operations and consequently cannot be optimized away.

public final int DURATION=10000; // In milliseconds

public void nop() throws InterruptedException {
  while (true) {
    // Useful operations
    Thread.sleep(DURATION);
  }
}

Compliant Solution (yield())

This compliant solution invokes Thread.yield(), which causes the thread running this method to consistently defer to other threads:

public void nop() {
  while (true) {
    Thread.yield();
  }
}

Risk Assessment

Automated Detection

Tool	Version	Checker	Description
Parasoft Jtest		CERT.MSC01.EB	Avoid control statements with empty bodies
SonarQube	3.10	S2189

Bibliography