for (String coordinate : coordinates)
时间: 2024-02-16 21:00:04 浏览: 19
这是 Java 中的 foreach 循环语句,也称为增强型 for 循环。它用于遍历数组或集合中的元素,可以简化代码的编写和阅读。
其中,`coordinates` 是一个字符串数组,`String` 表示数组元素的类型,`coordinate` 表示数组中的每一个元素。在循环的每一次迭代中,`coordinate` 会依次取到数组中的每一个元素,然后执行循环体中的语句。
例如,如果 `coordinates` 数组中有三个元素,分别是 `"1,2"`, `"3,4"`, `"5,6"`,那么循环语句:
```java
for (String coordinate : coordinates) {
System.out.println(coordinate);
}
```
会依次输出:
```
1,2
3,4
5,6
```
需要注意的是,foreach 循环只适用于遍历数组或集合中的元素,不适用于其他类型的数据结构。
相关问题
有一个文本文件记录许多坐标信息 现在C++中编写代码将坐标信息转换为规范化坐标系下的坐标 并且将转化后的坐标重新输入到新的坐标文件中 利用新的坐标文件输出图像并对图像进行一定比例的放大 最后要利用easyx的可视化功能显示出来 要求编写代码
好的,下面是一个简单的实现代码:
```c++
#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
#include <opencv2/opencv.hpp>
#include <graphics.h>
using namespace std;
using namespace cv;
// 规范化坐标系下的宽度和高度
const int norm_width = 800;
const int norm_height = 800;
// 读取原始坐标文件
vector<Point2f> read_coordinates(string filename) {
ifstream infile(filename);
vector<Point2f> coordinates;
string line;
while (getline(infile, line)) {
float x, y;
sscanf(line.c_str(), "%f,%f", &x, &y);
coordinates.push_back(Point2f(x, y));
}
return coordinates;
}
// 将坐标转换为规范化坐标系下的坐标
Point2f normalize_coordinate(Point2f coordinate, int width, int height) {
float nx = (coordinate.x - width / 2.0) / (width / 2.0);
float ny = (height / 2.0 - coordinate.y) / (height / 2.0);
return Point2f(nx, ny);
}
// 将规范化坐标系下的坐标转换为图像坐标系下的坐标
Point2f denormalize_coordinate(Point2f coordinate, int width, int height) {
float x = (coordinate.x + 1) * width / 2.0;
float y = height / 2.0 - (coordinate.y + 1) * height / 2.0;
return Point2f(x, y);
}
// 转换坐标并保存到新文件中
void save_normalized_coordinates(string input_filename, string output_filename) {
// 读取原始坐标文件
vector<Point2f> coordinates = read_coordinates(input_filename);
// 转换坐标为规范化坐标系下的坐标
vector<Point2f> normalized_coordinates;
for (auto coordinate : coordinates) {
normalized_coordinates.push_back(normalize_coordinate(coordinate, norm_width, norm_height));
}
// 保存规范化坐标到新文件中
ofstream outfile(output_filename);
for (auto coordinate : normalized_coordinates) {
outfile << coordinate.x << "," << coordinate.y << endl;
}
outfile.close();
}
// 生成图像并放大
void generate_image(string filename, float scale) {
// 读取规范化坐标文件
vector<Point2f> normalized_coordinates = read_coordinates(filename);
// 将规范化坐标转换为图像坐标
vector<Point2f> image_coordinates;
for (auto coordinate : normalized_coordinates) {
image_coordinates.push_back(denormalize_coordinate(coordinate, norm_width, norm_height));
}
// 创建图像
Mat image(norm_height, norm_width, CV_8UC3, Scalar(255, 255, 255));
for (auto coordinate : image_coordinates) {
circle(image, coordinate, 2, Scalar(0, 0, 255), -1);
}
// 调整图像大小
Mat scaled_image;
resize(image, scaled_image, Size(), scale, scale);
// 显示图像
namedWindow("Image", WINDOW_NORMAL);
imshow("Image", scaled_image);
waitKey(0);
}
// 显示图像
void show_image(string filename, float scale) {
// 生成图像并放大
generate_image(filename, scale);
// 显示图像
initgraph(norm_width * scale, norm_height * scale);
putimage(0, 0, (BYTE*)GetImageBuffer(), SRCCOPY);
closegraph();
}
int main() {
// 转换坐标并保存到新文件中
save_normalized_coordinates("coordinates.txt", "normalized_coordinates.txt");
// 显示图像
show_image("normalized_coordinates.txt", 2.0);
return 0;
}
```
这个代码实现了将坐标信息转换为规范化坐标系下的坐标,并将转换后的坐标重新输入到新的坐标文件中。然后,它使用OpenCV生成图像并对图像进行一定比例的放大。最后,它使用easyx的可视化功能显示生成的图像。
注意,这个代码依赖于OpenCV和easyx库,请确保你已经正确安装了这些库并将它们添加到了你的项目中。
用java写一段程序,需求1:读取excel中的x与y轴坐标值以及对应的高度。需求2:赋予每个坐标点3种状态,初始状态为0 需求3:读取excel表格中的风速风向数据,根据给定的计算公式计算蔓延因子 需求4:给定初始起火点,即状态从0到1,给定初始速度,乘以蔓延因子得到八个方向上的蔓延速度,乘以时间步长5分钟,得到新的蔓延范围
以下是Java程序示例,可供参考:
需求1:读取excel中的x与y轴坐标值以及对应的高度。
```
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
public class ReadExcel {
public static void main(String[] args) throws IOException {
FileInputStream inputStream = new FileInputStream(new File("data.xlsx"));
Workbook workbook = WorkbookFactory.create(inputStream);
Sheet sheet = workbook.getSheetAt(0);
for (Row row : sheet) {
Cell xCell = row.getCell(0);
Cell yCell = row.getCell(1);
Cell heightCell = row.getCell(2);
double x = xCell.getNumericCellValue();
double y = yCell.getNumericCellValue();
double height = heightCell.getNumericCellValue();
System.out.println("X: " + x + ", Y: " + y + ", Height: " + height);
}
workbook.close();
inputStream.close();
}
}
```
需求2:赋予每个坐标点3种状态,初始状态为0
```
import java.util.ArrayList;
import java.util.List;
public class Coordinate {
private double x;
private double y;
private double height;
private List<Integer> states;
public Coordinate(double x, double y, double height) {
this.x = x;
this.y = y;
this.height = height;
this.states = new ArrayList<>();
this.states.add(0);
this.states.add(0);
this.states.add(0);
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public double getHeight() {
return height;
}
public List<Integer> getStates() {
return states;
}
public void setStates(List<Integer> states) {
this.states = states;
}
}
```
需求3:读取excel表格中的风速风向数据,根据给定的计算公式计算蔓延因子
```
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
public class SpreadFactor {
private double windSpeed;
private double windDirection;
private double temperature;
private double humidity;
private double spreadFactor;
public SpreadFactor(double windSpeed, double windDirection, double temperature, double humidity) {
this.windSpeed = windSpeed;
this.windDirection = windDirection;
this.temperature = temperature;
this.humidity = humidity;
this.spreadFactor = 0;
}
public double calculate() {
// 根据给定的计算公式计算蔓延因子
// ...
return spreadFactor;
}
public static void main(String[] args) throws IOException {
FileInputStream inputStream = new FileInputStream(new File("data.xlsx"));
Workbook workbook = WorkbookFactory.create(inputStream);
Sheet sheet = workbook.getSheetAt(1);
for (Row row : sheet) {
Cell windSpeedCell = row.getCell(0);
Cell windDirectionCell = row.getCell(1);
Cell temperatureCell = row.getCell(2);
Cell humidityCell = row.getCell(3);
double windSpeed = windSpeedCell.getNumericCellValue();
double windDirection = windDirectionCell.getNumericCellValue();
double temperature = temperatureCell.getNumericCellValue();
double humidity = humidityCell.getNumericCellValue();
SpreadFactor spreadFactor = new SpreadFactor(windSpeed, windDirection, temperature, humidity);
double factor = spreadFactor.calculate();
System.out.println("Wind Speed: " + windSpeed + ", Wind Direction: " + windDirection
+ ", Temperature: " + temperature + ", Humidity: " + humidity
+ ", Spread Factor: " + factor);
}
workbook.close();
inputStream.close();
}
}
```
需求4:给定初始起火点,即状态从0到1,给定初始速度,乘以蔓延因子得到八个方向上的蔓延速度,乘以时间步长5分钟,得到新的蔓延范围
```
import java.util.ArrayList;
import java.util.List;
public class Spread {
private List<Coordinate> coordinates;
private double initialSpeed;
private double timeStep;
public Spread(List<Coordinate> coordinates, double initialSpeed, double timeStep) {
this.coordinates = coordinates;
this.initialSpeed = initialSpeed;
this.timeStep = timeStep;
}
public void ignite(int x, int y) {
for (Coordinate coordinate : coordinates) {
if (coordinate.getX() == x && coordinate.getY() == y) {
List<Integer> states = coordinate.getStates();
states.set(0, 1);
states.set(1, 0);
states.set(2, 0);
}
}
}
public void spread(double spreadFactor) {
List<Coordinate> newCoordinates = new ArrayList<>();
for (Coordinate coordinate : coordinates) {
List<Integer> states = coordinate.getStates();
if (states.get(0) == 1) {
double speed = initialSpeed * spreadFactor * timeStep;
double x = coordinate.getX();
double y = coordinate.getY();
double height = coordinate.getHeight();
newCoordinates.add(new Coordinate(x - speed, y, height));
newCoordinates.add(new Coordinate(x - speed, y + speed, height));
newCoordinates.add(new Coordinate(x, y + speed, height));
newCoordinates.add(new Coordinate(x + speed, y + speed, height));
newCoordinates.add(new Coordinate(x + speed, y, height));
newCoordinates.add(new Coordinate(x + speed, y - speed, height));
newCoordinates.add(new Coordinate(x, y - speed, height));
newCoordinates.add(new Coordinate(x - speed, y - speed, height));
} else if (states.get(0) == 0 && (states.get(1) == 1 || states.get(2) == 1)) {
// 根据给定的规则计算状态变化
// ...
newCoordinates.add(coordinate);
} else {
newCoordinates.add(coordinate);
}
}
coordinates = newCoordinates;
}
public static void main(String[] args) {
List<Coordinate> coordinates = new ArrayList<>();
coordinates.add(new Coordinate(0, 0, 10));
coordinates.add(new Coordinate(0, 1, 20));
coordinates.add(new Coordinate(0, 2, 30));
coordinates.add(new Coordinate(1, 0, 40));
coordinates.add(new Coordinate(1, 1, 50));
coordinates.add(new Coordinate(1, 2, 60));
coordinates.add(new Coordinate(2, 0, 70));
coordinates.add(new Coordinate(2, 1, 80));
coordinates.add(new Coordinate(2, 2, 90));
Spread spread = new Spread(coordinates, 10, 5);
spread.ignite(1, 1);
spread.spread(0.5);
}
}
```