我正在通过JDBC连接从PostgreSQL数据库中的表中检索结果集，如下所示：
"501.511346, 503.472045, 505.447591, 501.192024, 504.137371, 500.790352, 506.726137, 508.266889, 506.879129, 503.036632"
"506.233533, 504.731789, 507.639155, 507.187112, 501.124606, 508.558729,504.037900, 505.246124, 505.314278, 500.101784"
"509.075946, 505.219091, 505.953530, 501.323737, 509.691705, 500.110447, 505.315793, 503.922326, 505.259513, 507.176139"
"505.161837, 501.063333, 503.402369, 503.944111, 502.329003, 501.593900, 508.902708, 503.022083, 505.456198, 500.821379"
"501.136874, 507.282628, 501.076124, 504.313085, 502.092685, 504.601038, 508.905852, 507.602457, 502.363248, 501.228881"
"507.790364, 500.034138, 501.491094, 507.916393, 501.683380, 503.665745, 507.908477, 504.317156, 504.921323, 508.663319"
"501.013448, 501.443771, 500.449935, 501.570703, 501.112750, 507.936670, 506.626647, 504.746571, 501.478473, 505.641617"
"501.553313, 502.492668, 504.332290, 503.666099, 506.629541, 500.592711, 500.896930, 502.970319, 501.116483, 504.481986"
"502.187111, 502.145824, 509.532465, 500.348489, 503.842839, 508.749411, 500.718773, 508.422647, 508.683536, 505.489182"
"509.526615, 504.127884, 503.502820, 506.184630, 507.451289, 507.783623, 503.639020, 506.767338, 506.089402, 506.095711"
"505.050268, 504.379683, 508.883864, 508.821655, 506.592373, 507.762016, 503.664888, 507.020359, 502.166903, 504.881668"
"503.641401, 502.152418, 501.656423, 509.706045, 505.032023, 509.798445, 507.760368, 502.113529, 507.615546, 506.032260"
"506.855262, 508.673852, 503.902280, 507.339752, 509.106561, 503.817907, 504.675336, 502.857339, 505.761561, 505.328955"
"509.216366, 503.236089, 509.705565, 500.589984, 500.818828, 505.180683, 503.657360, 505.528898, 509.506768, 502.728268"
"507.932913, 505.611162, 500.728144, 502.882686, 500.979144, 506.991179, 500.943360, 506.693182, 508.148536, 508.699568"
"508.946498, 501.745562, 502.265949, 503.192731, 502.030673, 507.678642, 500.089286, 504.847314, 507.204066, 500.696839"
"507.151703, 505.898623, 508.330869, 504.758373, 503.307971, 500.713862, 506.714869, 503.989853, 508.461387, 507.387292"
"508.271230, 507.405013, 502.357225, 506.591855, 504.613121, 504.768269, 501.416726, 505.613160, 501.375562, 501.625350"
"504.183084, 507.494983, 505.040833, 505.075503, 504.161549, 500.649583, 507.194630, 503.392844, 505.336177, 508.217170"
"508.924550, 503.218437, 504.534036, 505.692131, 508.263250, 503.923185, 507.255442, 506.786683, 501.893640, 503.278230"
"506.812050, 500.469390, 506.258835, 500.542808, 502.774340, 506.703418, 504.855838, 508.988294, 504.825021, 503.711878"
"504.940812, 508.431433, 507.301498, 505.920257, 501.246557, 501.256791, 500.599958, 502.064444, 500.933950, 501.989907"
"500.374969, 504.333468, 501.590108, 504.684638, 501.577986, 507.462334, 503.769062, 501.015270, 506.213296, 504.483580"
"504.733616, 506.757830, 503.770166, 505.921616, 505.463712, 503.765199, 502.936621, 502.479458, 507.342924, 508.919453"
"509.786083, 504.510082, 501.687019, 509.471297, 503.188882, 507.377933, 508.997906, 509.912943, 504.786779, 503.013641"
"503.474216, 504.125196, 505.592858, 506.826637, 505.118236, 500.803693, 502.614498, 500.703702, 506.820342, 504.832302"
"500.387248, 504.569592, 502.562114, 504.589547, 508.552309, 509.541123, 500.961317, 501.182442, 508.204940, 505.628783"
"501.791401, 502.100932, 501.150022, 509.534479, 508.850065, 502.757766, 507.866282, 500.849425, 509.927472, 500.098215"
"504.735886, 509.656796, 500.461879, 500.453160, 508.434995, 506.671135, 500.992930, 505.550642, 507.093285, 503.311201"
不幸的是，此结果集中的每一行都是一个长逗号分隔的字符串。然而，这不是问题，因为我在我的java代码中解析返回到双精度数组中的每一行。我的最终目标是从此结果集创建一个二维2D数组。以下是我为此目的编写的方法，目前代表：
public double[][] getMatrix(int x, int y) {
int row = getRowDim(x, y); //separate method to get row dimension
int col = getColDim(x, y); //separate method to get column dimension
double[][] matrix = new double[row][col];
String[] intermediateArray = new String[col];
String px = "";
try {
conn = dataSource.getConnection();
} catch (SQLException e1) {
e1.printStackTrace();
}
try {
PreparedStatement p = conn.prepareStatement(getMatrix); //getMatrix query called from SQL prop file
p.setInt(1, x);
p.setInt(2, y);
ResultSet r = p.executeQuery();
int count=0;
while(r.next())
{
px = r.getString("prices");
intermediateArray = px.split(",", -1);
}
parsed = new double[intermediateArray.length];
for (int i = 0; i<intermediateArray.length; i++) {
parsed[i] = Double.valueOf(intermediateArray[i]);
}
for(int i=0;i<row;i++){
for(int j=0;j<col;j++){
if(count==parsed.length) break;
matrix[i][j]=parsed[(count)];
count++;
}
}
conn.close();
} catch (SQLException e) {
logger.error("***** SQL EXCEPTION *****");
e.printStackTrace();
}
return matrix;
}
这确实会返回一个具有正确维度的矩阵，但是只有结果集的最后一行被写入结果矩阵的第一行，如下所示：
504.74 509.66 500.46 500.45 508.43 506.67 500.99 505.55 507.09 503.31
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
在其他地方填充零值。我很确定我错误地将其中一个环定位在某个地方，但是因为我的生活无法找到原因。如果有人能指出我正确的方向，我将非常感激。如果我遗漏了任何必要的细节，请询问，谢谢。
答案 0 :(得分：1)
如果您使用的是Java 8，则只需使用：
String[] intermediateArray = new String[col];
int index = 0;
while(r.next()){
intermediateArray[i++] = r.getString("prices");
}
double[][] matrix = Arrays.stream(intermediateArray)
.map(s -> Stream.of(s.split(",")).mapToDouble(Double::parseDouble).toArray())
.toArray(double[][]::new);
这个想法是：将所有结果放在一个数组或一个List中，然后使用我的代码将这个String数组转换为二维数组（ideone demo）
答案 1 :(得分：1)
您的代码中需要更改一些内容。在完成处理结果集之前，您无法确切知道要预期的行数（即使您明确查询特定行，您也宁愿使代码安全）。因此，您可能需要使用灵活长度的数据结构。
你的问题是你使用相同的变量并在while循环中覆盖它。以下是相同代码的略微修改版本：
int row = getRowDim(x, y);
int col = getColDim(x, y);
double[][] matrix; //length of array cannot be guaranteed before reading the result set.
try {
conn = dataSource.getConnection();
} catch (SQLException e1) {
e1.printStackTrace();
}
List<double[]> matrixList = new ArrayList<>(); //rather use an array list to avoid unexpected index errors
try {
PreparedStatement p = conn.prepareStatement(getMatrix);
p.setInt(1, x);
p.setInt(2, y);
ResultSet r = p.executeQuery();
while(r.next())
{
String px = r.getString("prices");
String[] intermediateArray = px.split(",", -1);
double[] parsed = new double[intermediateArray.length];
for (int i = 0; i < intermediateArray.length; i++) {
//use Double.parseDouble(String) to avoid unnecessary boxing/unboxing
parsed[i] = Double.parseDouble(intermediateArray[i]);
}
matrixList.add(parsed);
}
matrix = new double[matrixList.size()][];
conn.close();
int index = 0;
for(double[] currentRow: matrixList) {
matrix[index++] = currentRow;
}
return matrix;
} catch (SQLException e) {
logger.error("***** SQL EXCEPTION *****");
e.printStackTrace();
return new double[0][0];
}