You may try using below function provided that you are handeling windows with different titles.
private String mainWindowsHandle; // Stores current window handle
public static boolean swithToWindow(WebDriver driver,String title){
mainWindowsHandle = driver.getWindowHandle();
Set<String> handles = driver.getWindowHandles(); // Gets all the available windows
for(String handle : handles)
{
driver.switchTo().window(handle); // switching back to each window in loop
if(driver.getTitle().equals(title)) // Compare title and if title matches stop loop and return true
return true; // We switched to window, so stop the loop and come out of funcation with positive response
}
driver.switchTo().window(mainWindowsHandle); // Switch back to original window handle
return false; // Return false as failed to find window with given title.
}