问编码文本错误:无法使用字符集windows-1256对文本进行编码

EN

public class Point {
double x, y;
int counter=0; 

Point (double ex, double why){
x=ex;
y=why; 
counter++; }

public Distance (double x1, double y1) {
/* using Pythagoras c^2 = a^2 + b^2 
 where a is the horizontal distance (x − x1)
 and b is the vertical distance (y − y1)
 and c is the distance */
double a, b, c;
a = Math.pow(x - x1);
b = Math.pow(y - y1);
c = Math.sqrt(a + b);
}

public product (double x1, double y1) {
// using the dot product rule =>  A.B=(a1.b1)+(a2.b2)
double product = (x * y)+(x1 * y1);
}

public void setX (double ex){
x=ex; }

public void setY (double why) {
y=why ; } 

public double getX() {
return x; }

public double getY() {
return y; } 

public int getCounter() {
return counter; } 

} // end of class