java语言程序设计基础篇第九章编程练习题

1
 
import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Rectangle R1 = new Rectangle(40,4);
		Rectangle R2 = new Rectangle(35.9,3.5);
		System.out.println(R1.getArea() + "\n" + R2.getArea());
		System.out.println(R1.getPerimeter() + "\n" + R2.getPerimeter());
	}
}
 
class Rectangle{
	double width = 1;
	double height = 1;
	Rectangle() {
	}
	
	Rectangle(double h, double w){
		height = h;
		width = w;
	}
	
	double getArea(){
		return width*height;
	}
	
	double getPerimeter(){
		return 2*(width+height);
	}
	
}
 
2
 
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Stock obj = new Stock("ORCL","Oracle Corporation");
		obj.previousClosingPrice = 34.5;
		obj.currentPrice = 34.35;
		System.out.println(obj.getChangePercent());
	}
}
 
class Stock{
	String symbol;
	String name;
	double previousClosingPrice = 0.0;
	double currentPrice = 0.0;
	
	public Stock(String sym, String na){
		symbol = sym;
		name = na;
	}
	
	public String getChangePercent(){
		return Math.abs(((currentPrice-previousClosingPrice)/previousClosingPrice))*100+"%";
	}
}
 
3
 
import java.util.Scanner;
import java.util.Date;
 
public class Main{
	
	public static void main(String[] args){
		long num = 10000;
		Date date = new Date(num);
		System.out.println(date.toString());
		
		date.setTime(num*10);
		System.out.println(date.toString());
		
		date.setTime(num*100);
		System.out.println(date.toString());
		
		date.setTime(num*1000);
		System.out.println(date.toString());
		
		date.setTime(num*num);
		System.out.println(date.toString());
		
		date.setTime(num*num*10);
		System.out.println(date.toString());
		
		date.setTime(num*num*100);
		System.out.println(date.toString());
		
		date.setTime(num*num*1000);
		System.out.println(date.toString());
	}
}
 
4
 
import java.util.Scanner;
import java.util.Random;
 
public class Main{
	
	public static void main(String[] args){
		Random random = new Random(1000);
		for(int i = 0; i < 50; ++i){
			System.out.print(random.nextInt(100) + " ");
			if(i%10 == 0)
				System.out.println();
		}
	}
}
 
5
 
import java.util.Scanner;
import java.util.GregorianCalendar;
//我很纳闷为什么输出结果是一样的
public class Main{
	
	public static void main(String[] args){
		GregorianCalendar calendar = new GregorianCalendar();
		System.out.println(calendar.YEAR + ":" + calendar.MONTH + ":" + calendar.DAY_OF_MONTH);
 
		calendar.setTimeInMillis(1234567898765L);
		System.out.println(calendar.YEAR + ":" + calendar.MONTH + ":" + calendar.DAY_OF_MONTH);
	}
}
 
6
 
import java.util.Scann