怎样用java编写程序获取已知文件的扩展名.能否给出能够直接运行的代码呢

Answer 1

import java.io.File;
import java.io.IOException;

import javax.swing.JFileChooser;

public class Test {

public static void main(String[] args) throws IOException {

File file = null;
JFileChooser chooser = new JFileChooser();

if (chooser.showDialog(null, "Please choose the file") == JFileChooser.APPROVE_OPTION) {
file = chooser.getSelectedFile();
} else {
System.exit(0);
}

StringBuilder sb = new StringBuilder(file.getName()).reverse();

String ext = new StringBuilder(sb.substring(0, sb.indexOf("."))).reverse().toString();

System.out.println("文件扩展名为" + ext);

}
}