java例程练习（一个BirthDate类 以及简单的测试程序）

public class Test {public static void main(String[] args) {Test test = new Test();int date = 9;BirthDate d1 = new BirthDate(7, 7, 1970);BirthDate d2 = new BirthDate(1, 1, 2000);test.change1(date);test.change2(d1);test.change3(d2);System.out.println("date = " + date);d1.display();d2.display();}public void change1(int i) {i = 1234;}public void change2(BirthDate b) {b = new BirthDate (22, 2, 2004);}public void  change3(BirthDate b) {b.setDay(22);}}class BirthDate {private int day;private int year;private int month;BirthDate(int d, int y, int m) {day = d;year = y;month = m;}public void setDay(int day) {this.day = day;}public int getDay() {return day;}public void setYear(int year) {this.year = year;}public int getYear() {return year;}public void setMonth(int month) {this.month = month;}public int getMonth() {return month;}public void display() {System.out.println(day + "-" + month + "-" + year);}}