多边形Polygon.java
摘自高等教育出版社《Java程序设计(许满武 主编)》
class Polygon{
private Point[] vertices; //vertices域的类型为Point[]
//构造器
public Polygon(Point... vers){ //形参vers的类型为Point...(可变形参)
vertices=new Point[vers.length]; //确定数组大小,
for(int i=0;i<vertices.length;i++)
vertices[i]=vers[i]; //每个元素都是null
}
//打印所有点,逐元循环
public void print(){
for(Point p:vertices)
System.out.println(p);
}
public int getEdgeNum(){
return vertices.length;
}
//...
public static void main(String[] args){
Polygon triangle=new Polygon(new Point(11,22),new Point(22,33),new Point(33,22));
System.out.println(triangle.getEdgeNum());
triangle.print();
}
}
计算整数数组平均值Arraytest.java
class Arraytest{
static double average(int[] values){
if(values==null||values.length==0)//当第一个表达式为真,则不再判断第二个
throw new IllegalArgumentException();
else{
double sum=0.0;
for(int v:values)
sum+=v;
return sum/values.length;
}
}
public static void main(String[] args){
int[] data={11,22,33,44};
System.out.println(average(data));
}
}