It works for me too sir,
Am trying to understand the code ..
DesiredCapabilities cap = new DesiredCapabilities();
cap.setCapability(CapabilityType.BROWSER_NAME, "firefox");
cap.setCapability(CapabilityType.PROXY, proxy);
FirefoxDriver driver = new FirefoxDriver(cap);<--------------------------this "cap" here is not object reference of Capabilities class
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javadoc only says :FirefoxDriver(Capabilities desiredCapabilities)
Sir how did you come up with "cap" parameter in firefox constructor? "FirefoxDriver driver = new FirefoxDriver(cap);"