The Java Tutorials have been written for JDK 8.Java教程是为JDK 8编写的。Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.本页中描述的示例和实践没有利用后续版本中引入的改进，并且可能使用不再可用的技术。See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.有关Java SE 9及其后续版本中更新的语言特性的摘要，请参阅Java语言更改。
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.有关所有JDK版本的新功能、增强功能以及已删除或不推荐的选项的信息，请参阅JDK发行说明。
Here's the basic structure of the GenSig program. Place it in a file called GenSig.java.
import java.io.*;
import java.security.*;
class GenSig {
public static void main(String[] args) {
/* Generate a DSA signature */
if (args.length != 1) {
System.out.println("Usage: GenSig nameOfFileToSign");
}
else try {
// the rest of the code goes here
} catch (Exception e) {
System.err.println("Caught exception " + e.toString());
}
}
}
Notes:
The methods for signing data are in the java.security package, so the program imports everything from that package. The program also imports the java.io package, which contains the methods needed to input the file data to be signed.
A single argument is expected, specifying the data file to be signed.
The code written in subsequent steps will go between the try and the catch blocks.