try-catch

问题 Take this thread: Thread thread = new Thread(delegate() { //Code }); thread.Start(); Should it be around the thread.Start(); or inside: Thread thread = new Thread(delegate() { try { //Code } catch (Exception) { //Code } }); 回答1: it is completely different to put then inside or outside. If you put them around the thread.Start() call, you can detect (according to this page: http://msdn.microsoft.com/en-us/library/system.threading.thread.start(v=vs.71).aspx) ThreadStateException The thread has

问题 If I do something like try ( Connection conn = Database.getConnection(); PreparedStatement ps = conn.prepareStatement("SELECT * FROM table WHERE something = ? LIMIT 1"); ) { ps.setString(1, "hello world"); ResultSet results = ps.executeQuery(); if(results.next()) { // blah } } catch(SQLException e) { e.printStackTrace(); } Will the ResultSet still be closed when the PreparedStatement is closed, or will I still have to explicitly close the ResultSet also? 回答1: As per javax.sql.Statement.close(

问题 If I do something like try ( Connection conn = Database.getConnection(); PreparedStatement ps = conn.prepareStatement("SELECT * FROM table WHERE something = ? LIMIT 1"); ) { ps.setString(1, "hello world"); ResultSet results = ps.executeQuery(); if(results.next()) { // blah } } catch(SQLException e) { e.printStackTrace(); } Will the ResultSet still be closed when the PreparedStatement is closed, or will I still have to explicitly close the ResultSet also? 回答1: As per javax.sql.Statement.close(

问题 What are the pros and cons of using either of the following approaches to pulling out a double from an object? Beyond just personal preferences, issues I'm looking for feedback on include ease of debugging, performance, maintainability etc. public static double GetDouble(object input, double defaultVal) { try { return Convert.ToDouble(input); } catch { return defaultVal; } } public static double GetDouble(object input, double defaultVal) { double returnVal; if (double.TryParse(input.ToString(

问题 I am trying to put IFERROR condition in R like Excel IFERROR Function. I am building a random forest model. To fine tune, i use tuneRF function. It helps to give optimal mtry parameter. #Selecting Optimal MTRY parameter mtry <- tuneRF(dat3[, -36], dat3[,36], ntreeTry=1000, stepFactor=1.5,improve=0.01, trace=TRUE, plot=TRUE) best.m <- mtry[mtry[, 2] == min(mtry[, 2]), 1] SOMETIMES, the above function returns error if OOB error would not improve in different iterations. Error in if (Improve >

问题 I keep getting a compile error on the return menuFont line it says there is no variable menuFont. Could someone please tell how to fix this. import java.awt.Font; import java.awt.FontFormatException; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class loadFiles { Font getFont(){ try { Font menuFont = Font.createFont( Font.TRUETYPE_FONT, new FileInputStream("font.ttf")); } catch (FileNotFoundException e) { System.out.println("Cant find

问题 As I understand, the following 2 examples should do the same thing. Why is the 1st considered better? 1: try { riskyMethod(); } catch(Exception e) { //handle exception } finally { cleanUp(); } 2: try { riskyMethod(); } catch(Exception e) { //handle exception } cleanUp(); EDIT: The example is in Java, but I'm wondering about the concept of a finally block in general, as used in any language 回答1: Well, for one thing if the "handle exception" part throws an exception itself, cleanup won't occur.

问题 As I understand, the following 2 examples should do the same thing. Why is the 1st considered better? 1: try { riskyMethod(); } catch(Exception e) { //handle exception } finally { cleanUp(); } 2: try { riskyMethod(); } catch(Exception e) { //handle exception } cleanUp(); EDIT: The example is in Java, but I'm wondering about the concept of a finally block in general, as used in any language 回答1: Well, for one thing if the "handle exception" part throws an exception itself, cleanup won't occur.

问题 I have this piece of code import scala.util.Try val t: Try[Unit] = Try(Try(1)) and 2 questions: What is happening here? How can the type Try[Try[Int]] match with Try[Unit] ? Is it because Scala chooses the return type for block Try(1) to be Unit to match with the desired type? Is there anyway to detect a nested Try ? Says I have a Try[A] , how do I know if A is another Try[_] ? 回答1: You are basically forcing compiler to assign Try as Unit . For exmple doSomething method below is supposed to

问题 I have this piece of code import scala.util.Try val t: Try[Unit] = Try(Try(1)) and 2 questions: What is happening here? How can the type Try[Try[Int]] match with Try[Unit] ? Is it because Scala chooses the return type for block Try(1) to be Unit to match with the desired type? Is there anyway to detect a nested Try ? Says I have a Try[A] , how do I know if A is another Try[_] ? 回答1: You are basically forcing compiler to assign Try as Unit . For exmple doSomething method below is supposed to