It helps to resolve naming conflicts when different packages have classes with the same names. This also helps you prepare files within your project. As define: java.io package do something related to input output and java.net package do something to do with network and so on. If we toward to put all .java files into a single package, as the project gets larger, then it would become a nightmare to manage all your files. You may create a package as follows with package keyword, which is the first keyword in any Java program followed by import statements. The java.lang package is imported implicitly by default when a java program created and all the other packages must be explicitly imported when a java program created.
package com.xyz.client ;
import java.io.File;
import java.net.URL;