[求助]how to call a method from other java project file in eclipse

could anyone tell how to call a method from the other java project file by using eclipse? for example : there is one method called convert in the java project named lab2_1. u wanna use "convert" in the second java project named lab2_2. how could do this?? if anyone could help me solve the problem, i 'll appriciate very much! 3q!