课堂练习
package test; 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 W1 { public static void main(String[] args) throws IOException { try { //IO操作读取文件内容 FileReader fr = new FileReader("d:\\文件\\单词.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) { // TODO Auto-generated catch block e.printStackTrace(); } } }