Question

BirthDate.java程序错误在哪里运行不出来写着 c :\myjava>javac Test.java Test.java:46 找不到符号 符号

class BirthDate {
private int date;
private int month;
private int year;
public BirthDate(int d, int m, int y) {
day = d;
month = m;
year = y;
}
public void setDay(int d) {
day = d;
}

public void setMonth(int m) {
month = m;
}

public void setYear(int y) {
year = y;
}

public int getDay() {
return day;
}

public int getMonth() {
return month;
}

public int getYear() {
return year;
}

public void display() {
System.out.println(day + "-" + month + "-" + year);
}
}

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);
}
}
运行不出来，在c:\myjava\BirthDate\的Test.java目录下
错误结果是：
c:\myjava>javac Test.java
Test.java:46:找不到符号
符号：方法change1(int)
位置：类Test
test.change1(date);
有哪位能帮我看一下哪出错了

Answer 1

你的change1,2,有问题...你那个 i = 1234 以及 b = new BirthDate(22,2,2004) 都在方法内将变量指向了另外的地址...当参数为形参的时候...传到方法内的变量为副本...在方法内修改的也是副本的值...

修改如下...

public class Test {
public int change1() {
return 1234;
}
public BirthDate change2() {
BirthDate b = new BirthDate(22,2,2004);
return b;
}

public static void main(String args[]) {
Test test = new Test();
int date = 9; // a
BirthDate d1 = new BirthDate(7,7,1970); // b
BirthDate d2 = new BirthDate(1,1,2000);
test.change1(date); //将 a 处与此处合并为 int date = test.change1();
test.change2(d1); //将 b 处与此处合并为 BirthDate d1 = test.change2();
test.change3(d2);
System.out.println("date=" + date);
d1.display();
d2.display();
}

Answer 2

你在class BirthDate 根本没定义day
private int date;

public BirthDate(int d, int m, int y) {
day = d;
month = m;
year = y;
}

除了这里有问题 其他没问题

Answer 3

private int date; 改成private int day;