java.util.MissingFormatArgumentException

今天写了一段测试代码，以下：

package socStatistics;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Formatter;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

import org.apache.ibatis.io.Resources;

import socStatistics.entity.StatisticsResultData;

public class StatisticsMain {
	public static void main(String[] args) {

		// 最终
		Properties prop;
		try {
			prop = Resources.getResourceAsProperties("param.properties");
			String beginTime = (String) prop.get("beginTime");
			String endTime = (String) prop.get("endTime");
			List<StatisticsResultData> resultList = Utils
					.listStatisticResultDatas(beginTime, endTime);
			List<StatisticsResultData> rawlist = Utils.listStatisticResultDatas("0000",
					"2459");
			System.out.print("原始数据量=" + rawlist.size() + ", 符合" + beginTime + "-"
					+ endTime + "之间的数据量=" + resultList.size());
			Formatter f = new Formatter(System.out);
			f.format(",比例= %.2f" + (double) resultList.size() / rawlist.size() * 100);

			System.out.println("%");

		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	

}

结果测试时报错以下：

原始数据量=1935, 符合0830-1730之间的数据量=1852,比例= Exception in thread "main" java.util.MissingFormatArgumentException: Format specifier '%.2f'
	at java.util.Formatter.format(Unknown Source)
	at java.util.Formatter.format(Unknown Source)
	at socStatistics.StatisticsMain.main(StatisticsMain.java:31)

按照提示，31行发生错误，原来是

f.format(",比例= %.2f" + (double) resultList.size() / rawlist.size() * 100);这里的+，应该是逗号。即改为f.format(",比例= %.2f" ，(double) resultList.size() / rawlist.size() * 100);

另外，若是想在输出百分数时直接在后面加上%，如f.format(",比例= %.2f %" ，(double) resultList.size() / rawlist.size() * 100);会报错：

原始数据量=1935, 符合0830-1730之间的数据量=1852Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = '%'
	at java.util.Formatter.checkText(Unknown Source)
	at java.util.Formatter.parse(Unknown Source)
	at java.util.Formatter.format(Unknown Source)
	at java.util.Formatter.format(Unknown Source)
	at socStatistics.StatisticsMain.main(StatisticsMain.java:31)

能够另起一行，System.out.println("%");