for - java 作業作不出來！！ 請大大來就就我吧"""

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import java.util.*;

public class Circle {

private double radius;
private String color;
private static int number;

public Circle() {
this(5.0,"Blue");
}

public Circle(double radius) {
this(radius,"Yellow");
}

public Circle(double radius, String color) {
this.radius = radius;
this.color = color;
this.number += 1;
}

public void show () {
double area = (radius*radius) * 3.14;
System.out.println("半徑:"+this.radius+" 顏色:"+this.color+" 圓面積:"+area);
System.out.println("數量:"+this.number);
}

public static void main(String[] args) {
Circle circle1 = new Circle();
circle1.show();

Circle circle2 = new Circle(6.0);
circle2.show();

Circle circle3 = new Circle(4.0,"Red");
circle3.show();
}
}

[q738...@yahoo.com.tw]

主類別
import java.util.*;

public class mains {

public void show(student student) {
student.Print();
}

public double Avg(student[] student) {
int summary = 0;
for (int i=0; i<student.length; i++)
summary += student[i].getChi();
return summary/student.length;

}

public static void main(String[] args) {

Scanner in = new Scanner(System.in);
mains main = new mains();
System.out.println("請輸入學生數量");
int count = in.nextInt();
student[] student = new student[count];
for (int i=0; i<count; i++) {
System.out.println("請輸入第"+i+1+"位學生姓名");
String name = in.next();
System.out.println("請輸入第"+i+1+"學生國文成績");
int chisc = in.nextInt();
System.out.println("請輸入第"+i+1+"學生數學成績");
int engsc = in.nextInt();
student[i] = new student(name);
student[i].setScore(chisc,engsc);
}

for (int i=0; i<count; i++)
main.show(student[i]);

System.out.println("國文平均:"+main.Avg(student));
}
}

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學生類別
public class student {

private String name;
private double chi;
private double eng;
private static int counter;

public student () {
this("Dufault");
}

public student(String name) {
this.name = name;
counter += 1;
}

public void setScore(double chiscore,double engscore) {
this.chi = chiscore;
this.eng = engscore;
}

public double getChi() {
return this.chi;
}

public void Print() {
System.out.println("姓名:"+this.name+" 中文:"+this.chi+" 英文:"+this.eng+" 個
數:"+Number());
}

public static int Number() {
return counter;
}

}