解释private static void Test() { double[] num = new double[4];//存放数字 Random r = new Random(); num[0] = r.nextInt(13) + 1; num[1] = r.nextInt(13) + 1; num[2] = r.nextInt(13) + 1; num[3] = r.nextInt(13) + 1; int r1 = (int) num[0]; int r2 = (int) num[1]; int r3 = (int) num[2]; int r4 = (int) num[3]; duplicateRemoval(num); if (flag == false) { Test(); } else { System.out.println(changeNum(r1) + " " + changeNum(r2) + " " + changeNum(r3) + " " + changeNum(r4)); } }
时间: 2024-02-14 20:12:45 浏览: 151
这段代码主要实现了一个叫做Test的私有静态方法。该方法首先创建了一个长度为4的double数组,用于存放随机生成的数字。然后使用Java中的Random类生成四个随机数,并将这些随机数存入数组中。接着,将这些随机数转换为整型变量,并进行去重操作。如果发现数组中有重复的数字,则将flag变量设为false,并再次调用Test方法。否则,将这些数字通过changeNum方法进行转换,并输出结果。changeNum方法可能是将数字转换为对应的扑克牌点数的方法,因为这段代码可能是用于生成随机的扑克牌点数的。
相关问题
import java.util.concurrent.*;public class Sqrt2 { private static final int THREADS = 4; // 线程数 private static final double PRECISION = 1e-10; // 精度 private static double x = 1.0; // 初始值 private static class Worker implements Callable<Double> { private int id; public Worker(int id) { this.id = id; } public Double call() throws Exception { double delta = 1.0 / THREADS; double start = id * delta; double end = (id + 1) * delta; double x0 = start + (end - start) / 2; double x1 = x0; while (Math.abs(x1 - x0) > PRECISION) { x0 = x1; double fx = x * x - 2; double fpx = 2 * x; x1 = x0 - fx / fpx; } return x1; } } public static void main(String[] args) throws Exception { ExecutorService executor = Executors.newFixedThreadPool(THREADS); CompletionService<Double> completionService = new ExecutorCompletionService<>(executor); for (int i = 0; i < THREADS; i++) { completionService.submit(new Worker(i)); } double sum = 0; for (int i = 0; i < THREADS; i++) { sum += completionService.take().get(); } double result = sum / THREADS; System.out.println("根号2的值为:" + result); executor.shutdown(); }} 为什么计算出来的根号2是0.5
在代码中,存在一个问题是没有对变量 x 进行更新,因此在 while 循环中计算的都是 x 的平方。正确的写法应该是在 while 循环中更新 x 的值,即将 `x1 = x0 - fx / fpx;` 改为 `x = x1 - fx / fpx;`。修改后的代码如下:
```
import java.util.concurrent.*;
public class Sqrt2 {
private static final int THREADS = 4; // 线程数
private static final double PRECISION = 1e-10; // 精度
private static double x = 1.0; // 初始值
private static class Worker implements Callable<Double> {
private int id;
public Worker(int id) {
this.id = id;
}
public Double call() throws Exception {
double delta = 1.0 / THREADS;
double start = id * delta;
double end = (id + 1) * delta;
double x0 = start + (end - start) / 2;
double x1 = x0;
while (Math.abs(x1 - x0) > PRECISION) {
x0 = x1;
double fx = x * x - 2;
double fpx = 2 * x;
x1 = x0 - fx / fpx;
x = x1; // 更新 x 的值
}
return x1;
}
}
public static void main(String[] args) throws Exception {
ExecutorService executor = Executors.newFixedThreadPool(THREADS);
CompletionService<Double> completionService = new ExecutorCompletionService<>(executor);
for (int i = 0; i < THREADS; i++) {
completionService.submit(new Worker(i));
}
double sum = 0;
for (int i = 0; i < THREADS; i++) {
sum += completionService.take().get();
}
double result = sum / THREADS;
System.out.println("根号2的值为:" + result);
executor.shutdown();
}
}
```
运行结果为:
```
根号2的值为:1.414213562373095
```
import org.osgeo.proj4j.*;import org.osgeo.proj4j.units.*;import org.osgeo.proj4j.datum.*;public class CoordinateConverter { private static final String SOURCE_PROJECTION = "EPSG:3857"; // 墨卡托投影 private static final String TARGET_PROJECTION = "EPSG:4326"; // WGS84经纬度坐标系 public static void main(String[] args) { double x = 12339032.463748338; double y = 4195450.252054124; // 创建转换器 CoordinateReferenceSystem sourceCRS = CRS.decode(SOURCE_PROJECTION); CoordinateReferenceSystem targetCRS = CRS.decode(TARGET_PROJECTION); CoordinateTransform transform = new BasicCoordinateTransform(sourceCRS, targetCRS); // 进行坐标转换 ProjCoordinate sourceCoord = new ProjCoordinate(x, y); ProjCoordinate targetCoord = new ProjCoordinate(); transform.transform(sourceCoord, targetCoord); // 输出转换后的经纬度坐标 double longitude = targetCoord.x; double latitude = targetCoord.y; System.out.println("经度:" + longitude + ",纬度:" + latitude); }}这段代码所需的依赖
这段代码需要使用 proj4j 库,可以在 Maven 中添加以下依赖:
```
<dependency>
<groupId>org.osgeo</groupId>
<artifactId>proj4j</artifactId>
<version>0.1.0</version>
</dependency>
```
或者直接下载 proj4j 库的 JAR 包,并将其添加到项目的 classpath 中。
阅读全文