我正在尝试从数据库中获取两个随机 rowid。一切正常,但我有一种情况,只有一个 rowid。我想在我的 try/catch 上进行循环,直到数据库中出现第二个数字。
我做错了什么?谢谢
public void Kaslaimejo() {
String sql = "SELECT rowid FROM Zaidejai WHERE Pirmas < 4 ORDER BY random() LIMIT 2";
Integer value1 = null, value2 = null;
Integer judesiukas1 = null, judesiukas2 = null;
int a = 0;
int k = 15; // kiek kartu? Reikia infinity padaryti
for (a = 0; a < 3; a++) {
try {
Connection conn = Serveris.connect();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql)) {
if (rs.next()) {
value1 = rs.getInt("rowid");
if (rs.next()) {
value2 = rs.getInt("rowid");
PreparedStatement buvo = conn.prepareStatement("UPDATE Zaidejai SET Numeriukas = ? WHERE rowid = ?");
buvo.setInt(1, i);
buvo.setInt(2, value1);
int buvolala = buvo.executeUpdate ();
PreparedStatement buvo2 = conn.prepareStatement("UPDATE Zaidejai SET Numeriukas = ? WHERE rowid = ?");
buvo2.setInt(1, i);
buvo2.setInt(2, value2);
int buvolala2 = buvo2.executeUpdate ();//
i++;
}
System.out.println("Pirmas zaidejas" + value1); // atspausdina 1 random zaideja is duomenu bazes
System.out.println("Antras zaidejas" + value2); // atspausdina 2 random zaideja is duomenu bazes
}
} catch (SQLException e) {
a--;
//System.out.println(e.getMessage());
}
}
}
现在我的程序循环两次,然后给出SQLException
。如何循环我的程序直到没有SQLException
?
最佳答案
好吧,我试着写下我认为你想做的事情。 您会一直等待,直到有人在数据库中添加了至少两个条目。 您提取两个值,处理它们,然后再等待。
需要注意的几点:
1. 对象比较需要使用.equals()
而不是==
2. 您可能希望提供某种方法来打破我编写的无限循环 (while(true)
)。
3. 小心 null
值。它们可能会产生 NullPointerException。
4. 尝试将代码分解为方法。每个大代码块都可以进入每个自己的方法。
public void Kaslaimejo(){
String sql = "SELECT rowid FROM Zaidejai WHERE Pirmas < 4 ORDER BY random() LIMIT 2";
Integer judesiukas1 = null, judesiukas2 = null;
while(true) {
List<Integer> values = new ArrayList<>();
while (values.size() < 2) {
try (Connection conn = Serveris.connect();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql)) {
if( rs.next() ){
Integer value = rs.getInt("rowid");
values.add(value);
}
} catch (SQLException e) {
e.printStackTrace();
}
}
try( Connection conn = Serveris.connect()) {
PreparedStatement buvo = conn.prepareStatement("UPDATE Zaidejai SET Numeriukas = ? WHERE rowid = ?");
buvo.setInt(1, i);
buvo.setInt(2, values.get(0));
int buvolala = buvo.executeUpdate ();
PreparedStatement buvo2 = conn.prepareStatement("UPDATE Zaidejai SET Numeriukas = ? WHERE rowid = ?");
buvo2.setInt(1, i);
buvo2.setInt(2, values.get(1));
int buvolala2 = buvo2.executeUpdate ();//
i++;
}catch (SQLException e) {
e.printStackTrace();
}
Connection conn = Serveris.connect();
try {
PreparedStatement pstmt = conn.prepareStatement("SELECT Pirmas FROM Zaidejai WHERE rowid = ?");
PreparedStatement pstmt2 = conn.prepareStatement("SELECT Pirmas FROM Zaidejai WHERE rowid = ?");
pstmt.setInt(1, values.get(0));
pstmt2.setInt(1, values.get(1));
ResultSet myrsv = pstmt.executeQuery();
ResultSet myrsv2 = pstmt2.executeQuery();
{
if (myrsv.next()) {
judesiukas1 = myrsv.getInt("Pirmas");
if (myrsv2.next()) {
judesiukas2 = myrsv2.getInt("Pirmas");
}
}
//System.out.println("Pirmo zaidejo veiksmas" + myrsv.getInt("Pirmas"));
//System.out.println("Antro zaidejo veiksmas" + myrsv2.getInt("Pirmas"));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (judesiukas1.equals(judesiukas2)) // careful here. NullPointerException may happen.
{
try {
PreparedStatement laim = conn.prepareStatement("UPDATE Zaidejai SET Rezultatas = ? WHERE rowid = ?"); // ble ble update reikia naudoti , o ne insert into. Insert kai sukuriame nauja kazka tik
PreparedStatement laim2 = conn.prepareStatement("UPDATE Zaidejai SET Rezultatas = ? WHERE rowid = ?");
laim.setString(1, "Lygiosios");
laim.setInt(2, values.get(0));
laim2.setString(1, "Lygiosios");
laim2.setInt(2, values.get(1));
int irasyk = laim.executeUpdate (); // kodel executeupdate, o ne executequery????
int irasyk2 = laim2.executeUpdate (); // kodel executeupdate, o ne executequery????
{
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.print("Lygiosios");
} else {
// (1) - Rock
// (2) Scissors
// (3) - Paper
switch (values.get(0)){
case 1:
if (judesiukas2 == 2)
System.out.print("Zaidejas 1 wins!");
else
System.out.print("Zaidejas 2 wins!");
break;
case 2:
if (judesiukas2 == 3)
System.out.print("Zaidejas 1 wins!");
else
System.out.print("Zaidejas 2 wins!");
break;
case 3:
if (judesiukas2 == 1)
System.out.print("Zaidejas 1 wins!");
else
System.out.print("Zaidejas 2 wins!");
break;
}
}
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
关于java - 循环try/catch语句,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53923829/