对象的构造和初始化过程演示.ppt

对象的构造和初始化过程示例 Student s1;---为引用类型变量分配引用空间 new Student (”Lisa“,”Male“,1,18); 创建新对象，并进行属性(实例变量)的默认初始化 执行构造方法：将传递进来的参数的值分别赋给对象属性 对引用类型变量s1赋值。将新创建的Student对象的存储空间的首地址赋给s1 演示 Student s1; s1=new Student (“Lisa”, “Male”,1,18); 实 例（1） 实 例（2） 调用过程演示 null s1 null null 0 name sex grade 0 age “Lisa” “male” 1 18 0x1a4afb class BirthDate { private int day; 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 intVal = 9; BirthDate d1= new BirthDate(7,7,1970); BirthDate d2= new BirthDate(1,1,2000); test.change1(intVal ); test.change2(d1); test.change3(d2); System.out.println( intVal = + intVal ); 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);} } intVal=9; 7 - 7 - 1970 22 - 1 - 2000 intVal的值没有变 d1的值没有变 d2的值改变了 ? 堆内存 110925 test 9 intVal 587934 1970 7 7 d1 354752 2000 1 1 d2 main 栈内存 Test test = new Test(); int intVal = 9; BirthDate d1= new BirthDate(7,7,1970); BirthDate d2= new BirthDate(1,1,2000); test.change1(intVal); test.change2(d1); test.change3(d2); … … … 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);} 9 change1 i 1234 587934 b 2004 22 2 354752 b 204856 22