求够知识.JAVA程序设计

public class Test {
public static void main(String[] args){
System.out.println ("=====第一题=====");
double[] d =new double[]{1.0,2.0,2.0,4.5,6.5,7.5,8.5,9.5,10.5};
double sum=0;
for (int i = 0 ;i < d.length ; i++){
System.out.println ("数组中第"+i+"个值为:"+ d[i]);
sum+= d[i];
}
System.out.println ("数组中的平均值为:" + sum/d.length);
System.out.println ("=====第二题=====");
System.out.println ("以10为半径的圆的面积为:" + Math.PI *100 );
}
}

public class Test{
public static void main(String args[]){
double[] d={1.0，2.0，2.0，4.5，6.5，7.5，8.5，9.5，10.5};
System.out.println(Study.avarage(d));
double r=10;
System.out.println(area(r));
}
public static double avarage(double[] d){
double count=0;
for(int i=0;i<d.length;i++){
count+=d[i];
}
return count/d.length;
}
public static dou