public class MyClass{
final int MAXX=640, MAXY=480; // low-res (VGA)
int x, y; // current location
/** Construct a MyClass with x and y values */
MyClass(int x, int y) {
this.x = x;
this.y = y;
}
/** Construct a MyClass with default values */
MyClass() {
this(MAXX/2, MAXY/2); // Use the constructor above
}public String toString()
{
return "[" + x + "," + y + "]";
}/** Test main program */
public static void main(String[] av) {
System.out.println(new MyClass(300,100));
System.out.println(new MyClass());
}
}javac时报错：
error:
MyClass.java:15: Can't reference MAXX before the superclass constructor has be called.
this(MAXX/2, MAXY/2); // Use the constructor above
^
MyClass.java:15: Can't reference MAXY before the superclass constructor has be called.
this(MAXX/2, MAXY/2); // Use the constructor above
^
2 errors请问问题出在哪，好像是MAXX,MAXXY定义的问题，先谢过了
final int MAXX=640, MAXY=480; // low-res (VGA)
int x, y; // current location
/** Construct a MyClass with x and y values */
MyClass(int x, int y) {
this.x = x;
this.y = y;
}
/** Construct a MyClass with default values */
MyClass() {
this(MAXX/2, MAXY/2); // Use the constructor above
}public String toString()
{
return "[" + x + "," + y + "]";
}/** Test main program */
public static void main(String[] av) {
System.out.println(new MyClass(300,100));
System.out.println(new MyClass());
}
}javac时报错：
error:
MyClass.java:15: Can't reference MAXX before the superclass constructor has be called.
this(MAXX/2, MAXY/2); // Use the constructor above
^
MyClass.java:15: Can't reference MAXY before the superclass constructor has be called.
this(MAXX/2, MAXY/2); // Use the constructor above
^
2 errors请问问题出在哪，好像是MAXX,MAXXY定义的问题，先谢过了
MyClass() {
this(MAXX/2, MAXY/2); // Use the constructor above
}上面那句有问题，不明白你要做什么，改成：MyClass() {
this.x = MAXX/2;
this.y = MAXY/2;// Use the constructor above
}构造函数能对自身的一些成员变量做一些初始，感觉你的写法好像C＋＋
改成 static final int MAXX=640, MAXY=480;就可以了 !
这是什么意思能给菜鸟解释下吗???这里的this指带的是什么呀?
但建议使用：yaowenjie1981(小渣)的
MyClass() {
this.x = MAXX/2;
this.y = MAXY/2;// Use the constructor above
}
因为MAXX与MAXY变量是非静态成员属性, 因此只能在对象被创建了之后才可以调用, 但此时this(MAXX / 2, MAXY / 2);这一句, 由于你得先取得MAXX与MAXY的值后才能传递参数到this中, 所以这就属于在还没有调用超类的构造函数之前就要取得当前类的成员, 这当然是不允许的(因为当前对象还没有创建完成).
你可以将MAXX与MAXY定义成static的(至于是不是final无关紧要, 当然这取决于你是否想让它们可被修改), 这样就不会有问题了. 因为static成员不与对象相关联