My phone needs to charge for about only 2 and half hour, but I forgot so I charged my phone for about 3 and half hour. Then I noticed that my battery is easy to drain. When my phone is in 14% or below, it will tell me that I already need to charge but when I turn off my phone and turn it on again, it will go back to 16%. Also when my phone is already 100% charged and I turn it off and on again, it will be at 95% left. Can overcharging destroy a Xperia J or Android phone?
If an Android device is connected to a charger for a long period of time, with poor ventilation, this can contribute to overheating the device.
Apart from that, modern devices and batteries will stop charging when the battery is fully charged. There's a builtin failsafe that will cut off the power, as to prevent overcharging. Additionally there's is also a Short Circuit Protection.
As per your device in particular, you can read from the User's Manual (page 13):
Charging the phone over a long period of time, for example, overnight, does not damage the battery or the phone.