Commonly used packages in Java5 are:

Java Code:
import java.awt.*; // Common GUI elements.
import java.awt.event.*; // The most common GUI event listeners.
import javax.swing.*; // More common GUI elements.
import java.util.*; // Data structures (Collections), time, Scanner, etc classes.
import java.io.*; // Input-output classes.
import java.text.*; // Some formatting classes.
import java.util.regex.*; // Regular expression classes.