java wgs84转墨卡托

WGS84是一种地理坐标系，而墨卡托投影是一种平面坐标系。因此，将WGS84坐标系的经纬度转换为墨卡托坐标系需要进行投影变换。

Java中可以使用Proj4j库进行投影变换。以下是一个示例代码：

import org.osgeo.proj4j.CoordinateReferenceSystem;
import org.osgeo.proj4j.CRSFactory;
import org.osgeo.proj4j.ProjCoordinate;

public class WGS84ToMercatorConverter {
    private static final String WGS84 = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs";
    private static final String MERCATOR = "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext";

    private final CoordinateReferenceSystem wgs84;
    private final CoordinateReferenceSystem mercator;

    public WGS84ToMercatorConverter() {
        CRSFactory crsFactory = new CRSFactory();
        wgs84 = crsFactory.createFromParameters("WGS84", WGS84);
        mercator = crsFactory.createFromParameters("Mercator", MERCATOR);
    }

    public ProjCoordinate convert(double longitude, double latitude) {
        ProjCoordinate wgs84Coordinate = new ProjCoordinate(longitude, latitude);
        ProjCoordinate mercatorCoordinate = new ProjCoordinate();
        mercatorCoordinate.setCoordinateReferenceSystem(mercator);
        mercatorCoordinate = (ProjCoordinate) wgs84Coordinate.transform(wgs84, mercatorCoordinate);
        return mercatorCoordinate;
    }
}

在这个示例中，WGS84坐标系使用了Proj4j库中的参数字符串“+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs”，墨卡托坐标系使用了参数字符串“+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext”。

将经度和纬度作为参数传递给convert方法，该方法将返回对应的墨卡托坐标。