java程序设计-第03章 类和对象.pptVIP

* final修饰基本变量，即为常量，值无法改变；final修饰引用类型变量，该引用变量不能改变，即不能重新赋值，但对象内的成员可以改变 public class FinalEx { public static void main(String args[]){ final StudentTest stu1=new StudentTest(22,Tom); StudentTest stu2=new StudentTest(25,Jerry); //stu1=stu2就会出错 System.out.println(stu1的name:+stu1.sname+ stu1的age:+stu1.sage); stu1.setSname(Jerry); stu1.setSage(25); //这时stu1指向的对象属性值发生了改变 System.out.println(stu1的name:+stu1.sname+ stu1的age:+stu1.sage); } } final关键字 class StudentTest{ String sname; int sage; public StudentTest(int sage,String sname){ this.sage=sage; this.sname=sname; } public void setSname(String sname){ this.sname=sname; } public void setSage(int sage){ this.sage=sage; } } final关键字 * class StudentFinal{ private final long StudentID; private static long number=2007030801; public StudentFinal (){ StudentID = number++; } public long getID(){ return StudentID; } public static void main(String[] args){ StudentFinal [ ] s = new StudentFinal [5]; for ( int i=0; is.length; i++){ s[i]=new StudentFinal (); System.out.println(The StudentID is +s[i].getID()); } } } 例:声明类的final变量并在构造方法中赋值 输出结果： The StudentID is 2007030801 The StudentID is 2007030802 The StudentID is 2007030803 The StudentID is 2007030804 The StudentID is 2007030805 class StudentFinal{ private final long StudentID private static long number=2007030801; public StudentFinal (){ StudentID = number++; } public long getID(){ return StudentID; } public static void main(String[] args){ StudentFinal [ ] s = new StudentFinal [5]; for ( int i=0; is.length; i++){