java遺珠之try-with-resources
阿新 • • 發佈:2019-02-04
try-with-resources語句自動關閉實現了AutoCloseable
或者 Closeable
介面的資源,示例如下:
public static void writeToFileZipFileContents(String zipFileName, String outputFileName) throws java.io.IOException {
java.nio.charset.Charset charset =
java.nio.charset.StandardCharsets.US_ASCII;
java.nio.file.Path outputFilePath =
java.nio.file.Paths.get(outputFileName);
// Open zip file and create output file with
// try-with-resources statement
try (
java.util.zip.ZipFile zf =
new java.util.zip.ZipFile(zipFileName);
java.io.BufferedWriter writer =
java.nio.file. Files.newBufferedWriter(outputFilePath, charset)
) {
// Enumerate each entry
for (java.util.Enumeration entries =zf.entries();entries.hasMoreElements();) {
// Get the entry name and write it to the output file
String newLine = System.getProperty("line.separator" );
String zipEntryName = ((java.util.zip.ZipEntry)entries.nextElement()).getName() +
newLine;
writer.write(zipEntryName, 0, zipEntryName.length());
}
}
}
這樣會抑制resouce中的異常,如果想看其中發生的異常,還可以增加catch和finally模組,示例如下:
public static void viewTable(Connection con) throws SQLException {
String query = "select COF_NAME, SUP_ID, PRICE, SALES, TOTAL from COFFEES";
try (Statement stmt = con.createStatement()) {
ResultSet rs = stmt.executeQuery(query);
while (rs.next()) {
String coffeeName = rs.getString("COF_NAME");
int supplierID = rs.getInt("SUP_ID");
float price = rs.getFloat("PRICE");
int sales = rs.getInt("SALES");
int total = rs.getInt("TOTAL");
System.out.println(coffeeName + ", " + supplierID + ", " +
price + ", " + sales + ", " + total);
}
} catch (SQLException e) {
JDBCTutorialUtilities.printSQLException(e);
}
}
但要注意的是,catch和finally都會等到資源關閉之後才執行。