Current Source and Voltage source

A current source is a device that provides constant current irrespective of the load applied to it.A current source can be made by using  a constant voltage regulator and  resistor in series which determines the amount of current flowing.We can use lm317to make a current source of 1A.These current sources have the applications  in electronic circuits and in battery chargers.
Similarly a voltage source is the circuit that provides constant voltage in the circuit connected linear voltage regulators and switched mode power supply will provide constant voltage by using electronic components