YOu can try this step if the above mentioned steps fails to help you and you have android device/windows PC which is previously connected to the network
check the windows wireless adapter properties for getting the wifi key
or you can check the following path in your android folder. data/misc/wifi and open the wpa_supplicant.conf file , You can find the ssid followed by the pass phrase of your wifi network (the device must be a rooted one
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