Clear defaults selenium java method

public ReleaseRequirePage setContactNumber(String phoneNum) {

　　WebElement element=tp.xpathLocator(TradingHallLoc.acontactNumber);
　　element.click();
　　element.sendKeys(Keys.chord(Keys.CONTROL, "a"));//全选
　　element.sendKeys(Keys.BACK_SPACE);//退格键删除
　　element.sendKeys(phoneNum);
　　return this;
}