3.在 Textpad（或Jcreator或UltraEdit）环境下编写一个HelloWorld.java程序，该程序在控制台输出HelloWorld字符串，在DOS提示符下编译并执行这个程序。

4.编写一个类A，它位于包a中，保存到A.java中，再编写一个类B，它位于包b中，保存到B.java中。在类B中实例化类A的一个对象。分别编译类A和类B。-3. Textpad (or Jcreator or UltraEdit) to prepare an environmental HelloWorld.java program that string in the console output HelloWorld in the DOS prompt to compile and run this program. 4. Write a class A, which is located in a package, save it to A.java in, then write a class B, which is located in the package b, save in the B.java. Instantiated in the class B, class A, an object. Compile class A and class, respectively, B.