求助， 怎么判断主函数参数的中的减号
题目要求是
java -jar word-counts.jar <-a|-c> <input_filename> <output_filename>
input_filename -- is a relative or absolute path to the input file to process,
or '-' to indicate input should be read from stdin
output_filename -- relative or absolute path to the output file to write the results to,
or '-' to indicate input should written to stdout
-a -- output words and counts ordered alphabetically by the words
-c -- output words and counts ordered by count descending
在函数中怎么检测“-”号是否存在，“-”号如果存在的话怎么检测后面参数是a还是c
[解决办法]
无论"-a"还是"-c"都是是一个字符串。参考String类。
[解决办法]
public static void main(String[] args) {
String tt = "java -jar word-counts.jar -a <input_filename> <output_filename>";
if (tt.contains("-a")) {
System.err.println("aaaaa");
} else if(tt.contains("-c")){
System.err.println("ccccccccccc");
}
}
run：
aaaaa
成功生成（总时间：0 秒）
[解决办法]
public class WordCount { public static void main(String[] args) { InputStream is = null; OutputStream os = null; boolean alphaOrder = true; if (args.length == 2 || args.length == 3) { int i = 0; if (args.length == 3) { if (args[0] == null) { // 输出错误信息 return; } switch (args[i++]) { case "-a": break; case "-c": alphaOrder = false; break; default: // 输出错误信息 return; } } if ("-".equals(args[i])) is = System.in; else try { is = new FileInputStream(args[i]); } catch (IOException ex) { ex.printStackTrace(); return; } i++; if ("-".equals(args[i])) os = System.out; else try { os = new FileOutputStream(args[i]); } catch (IOException ex) { ex.printStackTrace(); return; } } else { // 输出错误信息 return; } // 数据读写和单词计数部分自己可以写了吧 }}