Example:
boolean a = isRed();
boolean b = isLoud();;
if (a == b) {
System.out.println("Loudness correlates with redness");
}
More serious example:
boolean a = isRed();
boolean b = isLoud();
if (a == b) ;
System.out.println("Loudness correlates with redness");
Problem because:
Ugly
Can alter control-flow (though the real problem is am unbracjeted multiline if)
Severity: aesthetic to serious; usually not a bug, but can be