问题描述
我正在开发一个 Web 应用程序，在该应用程序中，数据将在客户端和客户端之间传输.服务器端.
I am working on a web application in which data will be transfer between client & server side.
我已经知道 JavaScript int != Java int.因为，Java int 不能为空，对.现在这是我面临的问题.
I already know that JavaScript int != Java int. Because, Java int cannot be null, right. Now this is the problem I am facing.
我将我的 Java int 变量更改为 Integer.
I changed my Java int variables into Integer.
public void aouEmployee(Employee employee) throws SQLException, ClassNotFoundException
{
Integer tempID = employee.getId();
String tname = employee.getName();
Integer tage = employee.getAge();
String tdept = employee.getDept();
PreparedStatement pstmt;
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/general";
java.sql.Connection con = DriverManager.getConnection(url,"root", "1234");
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
pstmt = (PreparedStatement) con.prepareStatement("REPLACE INTO PERSON SET ID=?, NAME=?, AGE=?, DEPT=?");
pstmt.setInt(1, tempID);
pstmt.setString(2, tname);
pstmt.setInt(3, tage);
pstmt.setString(4, tdept);
pstmt.executeUpdate();
}
我的问题在这里:
pstmt.setInt(1, tempID);
pstmt.setInt(3, tage);
我不能在这里使用整数变量.我试过 intgerObject.intValue();但它使事情变得更加复杂.我们还有其他转换方法或转换技术吗?
I cant use the Integer variables here. I tried with intgerObject.intValue();
But it makes things more complex. Do we have any other conversion methods or conversion techniques?
任何修复都会更好.
推荐答案
正如已经在别处写的:
- 对于 Java 1.5 及更高版本，您(几乎)不需要做任何事情，它由编译器完成.
- 对于 Java 1.4 及之前版本，使用
Integer.intValue()将 Integer 转换为 int.
- For Java 1.5 and later you don't need to do (almost) anything, it's done by the compiler.
- For Java 1.4 and before, use
Integer.intValue()to convert from Integer to int.
但是正如您所写，Integer 可以为空，因此在尝试转换为 int 之前检查一下是明智的(否则可能会遇到 NullPointerException).
BUT as you wrote, an Integer can be null, so it's wise to check that before trying to convert to int (or risk getting a NullPointerException).
pstmt.setInt(1, (tempID != null ? tempID : 0)); // Java 1.5 or later
或
pstmt.setInt(1, (tempID != null ? tempID.intValue() : 0)); // any version, no autoboxing
* 使用默认值零，也可以什么都不做，显示警告或...
我大多不喜欢使用自动装箱(第二个示例行)，所以很清楚我想要做什么.
I mostly prefer not using autoboxing (second sample line) so it's clear what I want to do.
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