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摘要: 构造函数的继承问题
class base{
}
class derived extends base{
public static void main(String[] args){
derived d=new derived();
}
}
class base{
base(){
System.out.println("base constructor");
}
}
class derived extends base{
derived(){
System.out.println("derived constructor");
}
public static void main(String[] args){
derived d=new derived();
}
}
执行结果如下:说明了先产生base class然后是derived class。
base constructor
derived constructor
class base{
base(){
System.out.println("base constructor");
}
base(int i){
System.out.println("base constructor int i");
}
}
class derived extends base{
derived(){
System.out.println("derived constructor");
}
derived(int i){
System.out.println("derived constructor int i");
}
public static void main(String[] args){
derived d=new derived();
derived t=new derived(9);
}
}
D:\java\thinking\think6>java derived
base constructor
derived constructor
base constructor
derived constructor int i
class base{
// base(){
// System.out.println("base constructor");
// }
base(int i){
System.out.println("base constructor int i");
}
}
class derived extends base{
derived(){
System.out.println("derived constructor");
}
derived(int i){
System.out.println("derived constructor int i");
}
public static void main(String[] args){
derived d=new derived();
derived t=new derived(9);
}
}
D:\java\thinking\think6>javac derived.java
derived.java:10: cannot resolve symbol
symbol : constructor base ()
location: class base
derived(){
^
derived.java:13: cannot resolve symbol
symbol : constructor base ()
location: class base
derived(int i){
^
2 errors
class base{
// base(){
// System.out.println("base constructor");
// }
base(int i){
System.out.println("base constructor int i");
}
}
class derived extends base{
derived(){
super(8);
System.out.println("derived constructor");
}
derived(int i){
super(i);
System.out.println("derived constructor int i");
}
public static void main(String[] args){
derived d=new derived();
derived t=new derived(9);
}
}
D:\java\thinking\think6>java derived
base constructor int i
derived constructor
base constructor int i
derived constructor int i