如果出于封装目的需要，可以在同一个源文件中定义多个类，如下例所示：
public class MultipleClassesInSameFile {
public static void main(String[] args) {
System.out.println(GenerateMessage.generateMessage());
System.out.println(AnotherMessage.generateAnotherMessage());
}
}
class GenerateMessage {
static String generateMessage() {
return "Here is one message";
}
}
class AnotherMessage {
static String generateAnotherMessage() {
return "Here is another message";
}
}
执行时：
$ java MultipleClassesInSameFile.java
将输出：
Here is one message Here is another message
