从另一个Java文件中的一个文件扩展Java类

只需将两个文件放在同一目录中即可。这是一个例子：

人.java

public class Person {  public String name;  public Person(String name) {    this.name = name;  }  public String toString() {    return name;  }}

学生.java

public class Student extends Person {  public String somethingnew;  public Student(String name) {    super(name);    somethingnew = "surprise!";  }  public String toString() {    return super.toString() + "t" + somethingnew;  }  public static void main(String[] args) {    Person you = new Person("foo");    Student me = new Student("boo");    System.out.println("Your name is " + you);    System.out.println("My name is " + me);  }}

运行Student（因为它具有主要功能）会为我们带来所需的结果：

Your name is fooMy name is boo  surprise!