Rain drawing (implemented in JAVA)
A new foreign teacher course, Object-oriented Programming (JAVA), records some learning experience, and some perceptions of the difference with C++. This article is a rainfall mapping job demo. The presumably requirement is to find the city entered by the user from the console from a .text file, and plot the 12-month rainfall data for that city. Requirements areYou cannot use containers such as arrays to store data in advance, Must be input. After user input, find the target city in the .text file and draw it. The text file format is as follows:
…
Beijing 20.8 52.4 67.3 22.3 55.0 76.3 20.8 52.4 67.3 22.3 55.0 76.3
…
- Start programming from main. Analyze requirements and modularize each part. Then fill, adjust, debug, etc.
- The readability of the code is very important (same as the teacher said at the beginning of the C++ memory management course)
- The throws FileNotFoundException / try catch mechanism is very useful to help analyze the problem of error reporting.
- For the data scanned in by Scanner, you need to use .next()/.nextInt() to convert the data type before performing the operation. And every time .next() is called, the cursor moves to the next space orTAB.
- java中.equals()
- The upper left corner of the DrawingPanel is the origin of the coordinate axis
My own summary and thinking, the current level is limited, if you have any suggestions, welcome to advise! code show as below:
package assignment;
import java.awt.*;
import java.util.*;
import java.io.*;
public class RainfallPlotter {
private static final int MONTH_WIDTH = 70;
private static final int NAME_WIDTH = 100;
private static final int HEIGHT = 550;
private static final int LINE_OFFSET = 25;
private static final int WIDTH = 12 * MONTH_WIDTH;
private static final Color[] COLORS = {
Color.RED, Color.BLUE, Color.GREEN };
// global para of color index
public static int I = -1;
private static final String STOP = "stop";
private static final String[] MONTHS_NAME = {
"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
// relative path
private static final String DATA_FILE = "./rainfall.txt";
// object panel is used in all process-life, and never changed.
private static final DrawingPanel panel = new DrawingPanel(WIDTH, HEIGHT);
// object g is used in three method of my solution.
private static final Graphics g = panel.getGraphics();
/**
* The main program
* Plus. If the user input the four city it will be wrong. Maybe use the para I
* as the while loop stop condition( || )can solve this question.
*/
public static void main(String[] args) throws FileNotFoundException {
menuOpen();
// draw the panel.(No data)
drawingPanel();
// Scanner for console input of user
Scanner consol_input = new Scanner(System.in);
do {
System.out.print("City? ");
} while( readDbFile(consol_input) );
consol_input.close();
menuClose();
}
private static void menuOpen()
{
System.out.println("Welcome to the Rainfall Plotter program!");
System.out.println("You can plot the rainfall for up to 3 cities");
System.out.println("You can stop plotting by entering 'stop' as the name of the city");
}
private static void menuClose()
{
System.out.println("Thank you for using the Rainfall Plotter program!");
}
//
private static boolean readDbFile(Scanner consol_input) throws FileNotFoundException
{
String answer = consol_input.nextLine().trim();
// Scanner for user input
if (answer.equals(STOP)) {
return false; } // 比 == 好用
// Scanner for load file
Scanner input_file = new Scanner(new File(DATA_FILE));
while ( input_file.hasNextLine() ) {
String line = input_file.nextLine();
// Scanner for every row
Scanner input_line = new Scanner(line);
//注意这里不可以直接用input_line与string比较
String city = input_line.next(); //每next一次都往下移
// find city
if (city.equals(answer)) // java 风格 相等
{
// draw point on the panel
drawingPoint(input_line, answer);
// scanner close. Draw over
input_line.close();
return true;
}
input_line.close();
}
input_file.close();
System.out.println("City not found.");
return true;
}
//
private static void drawingPoint(Scanner city, String answer)
{
// draw city name on the panel(avoid overlap too), and set the color.
// I is index of color.
++I;
g.setColor(COLORS[I]);
g.drawString(answer, NAME_WIDTH * I, LINE_OFFSET-5);
// i and j is index of month
int i = 0;
double temp_point_next = 0;
while ( city.hasNext() )
{
double temp_point = city.nextDouble();
drawNum(temp_point, i);
if (i != 0) {
drawColorLine(temp_point, temp_point_next, i, i-1); }
for (int j = i+1; j < i+2; j++)
{
temp_point_next = city.nextDouble();
drawNum(temp_point_next, j);
drawColorLine(temp_point, temp_point_next, i, j);
}
i = i + 2;
}
}
private static void drawColorLine(double temp_point, double temp_point_next, int i, int j)
{
int point1 = doubleToIntPoint(temp_point);
int point2 = doubleToIntPoint(temp_point_next);
g.drawLine(MONTH_WIDTH * i - 5, HEIGHT - (LINE_OFFSET + point1), MONTH_WIDTH * j -5, HEIGHT - (LINE_OFFSET + point2));
}
private static void drawNum(double temp_point, int i)
{
String num = String.valueOf(temp_point);
int point = doubleToIntPoint(temp_point);
g.drawString(num, MONTH_WIDTH * i, HEIGHT - (LINE_OFFSET + point));
}
private static int doubleToIntPoint(double target)
{
target = (target * 10) / 3;
int point = (int)target;
return point;
}
private static void drawingPanel()
{
g.drawLine(0, LINE_OFFSET, WIDTH, LINE_OFFSET);
g.drawLine(0, HEIGHT-LINE_OFFSET, WIDTH, HEIGHT-LINE_OFFSET);
for (int i = 0; i < MONTHS_NAME.length; i++)
{
g.drawString(MONTHS_NAME[i], MONTH_WIDTH * i, HEIGHT);
// "-5" to avoid "line" and "month text" overlap. For beauty
g.drawLine(MONTH_WIDTH * i - 5, LINE_OFFSET, MONTH_WIDTH * i -5, HEIGHT);
}
}
}