在工程编译时,编译器发现部分代码是无用代码,则会提示:某一行代码是DeadCode。今天compile工程的时候发现某一个循环出现这个问题,如下:
public void mouseOver(final String[] xpathArray) {
final int browserType = GlobalSettings.browserCoreType;
// Selenium doesn't support the Safari browser
if (browserType == 4) {
Assert.fail("Mouseover is not supported for Safari now");
Assert.fail("Incorrect browser type");
} pause(pause);
Robot rb = null;
try {
rb = new Robot();
} catch (AWTException e) {
e.printStackTrace();
}
rb.mouseMove(0, 0);
try {
webDriverWait.until(new ExpectedCondition<Boolean>() {
@Override
public Boolean apply(WebDriver driver) {
Boolean flag = false;
for (String xpath : xpathArray) {
WebElement we = findElement(xpath); if (browserType == 2 || browserType == 5 || browserType == 6) {
try {
Actions builder = new Actions(browserCore);
builder.moveToElement(we).build().perform();
flag = true;
break;
} catch (Exception e) {
logger.error("Failed to mouseover " + xpath, e);
flag = false;
handleFailure(e.getMessage());
}
logger.info("Mouseover " + xpath);
} else if (browserType == 1 || browserType == 3) {
try {
for (int i = 0; i < 5; i++) {//DeadCode
Actions builder = new Actions(browserCore);
builder.moveToElement(we).build().perform();
logger.info("Mouseover " + xpath);
flag = true;
break;
}
}catch (Exception e) {
logger.error("Failed to mouseover " + xpath, e);
flag = false;
handleFailure(e.getMessage());
}
}
}
return flag;
}
});
}catch (Exception e){
handleFailure(e.getMessage());
}
分析了下,其实循环部分的第二次就不会再执行了,因编译器已经检查到执行后的flag的状态为true,所以给出了DeadCode的警告。而代码实际运行过程中也确实不会执行第二次。
举个例子:
if(true && true){
System.out.println("这里会一直被执行");
}else{
System.out.println("这里一直不会被执行");
}
上例中,因compiler 已经判定if的结果只会为true,所以else中的语句永远不会被执行,因此else中为DeadCode。
无法预判的语句
Boolean a = true;
Boolean b = true;
if(a && b){
System.out.println("这里会一直被执行");
}else{
System.out.println("这里一直不会被执行");
}
上例中,由于a 和 b是2个变量,编译器编译时,无法预判if的结果是true,因此不会警告else的内容为DeadCode。