课堂测试一

package word_show;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

public class word{

public static void main(String[] args) throws IOException {
try {
//IO操作读取文件内容
FileReader fr = new FileReader("D:\\\\QQ Download\\\\java\\\\piao_english.txt");
BufferedReader br = new BufferedReader(fr);
NumberFormat nf = NumberFormat.getInstance();

// 设置精确到小数点后2位

nf.setMaximumFractionDigits(2);
HashMap<String, Integer> map = new HashMap<String, Integer>();

String string =null;
Integer count = 0;//每个字母的次数
Integer total = 0;//总共多少个字母

while ((string=br.readLine())!=null) {
char[] ch = string.toCharArray();

for (int i = 0; i < ch.length; i++) {
if (ch[i] > 'A' && ch[i]< 'z') {

total++;
ch[i] = Character.toLowerCase(ch[i]);
count = map.get(ch[i]+"");
if (count == null) {
count = 1;
}else {
count++;
}
map.put(ch[i]+"", count);
}
}
}
ArrayList<String> list = new ArrayList<String>();
list.addAll(map.keySet()); //将单词添加到list中

//排序按照出现次数降序排列
for(int i = 0;i < list.size();i++)
{

for(int j = 0;j < (list.size() - i-1);j++) //list.size() - i-1因为要用到i+1要考虑是否超出范围的问题
{

if(map.get(list.get(j)) < map.get(list.get(j+1)))
{
String t = list.get(j);
list.set(j, list.get(j+1));
list.set( j+1, t);
}
}
}
for(int i = 0 ; i < list.size();i++)
{
System.out.println(list.get(i) + ":" + map.get(list.get(i)) +" "+ nf.format((float)(map.get(list.get(i)))*100/total) + "%");
}


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

}