代码如下:没有加注释，自己研究吧。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

public class test2 {
public static void main(String[] args)throws IOException
{
List<Integer> list=new ArrayList<>();
DecimalFormat df=new DecimalFormat("######0.00");
File f = new File("piao1.txt");
FileInputStream fip = new FileInputStream(f);
InputStreamReader reader = new InputStreamReader(fip, "gbk");
StringBuffer sb = new StringBuffer();
while (reader.ready()) {
sb.append((char) reader.read());
}
System.out.println(sb.toString());
reader.close();
fip.close();
int i;
String A=sb.toString();
String M="abcdefghijklmnopqrstuvwxyz";
String temp = "";
char NUM[]=new char[A.length()];
char Z[]=new char[26];
int X[]=new int[26];
int MAX=0;
Z=M.toCharArray();
for(int k=0;k<26;k++)
{
X[k]=0;
for(i=0;i<A.length();i++)
{
NUM[i]=A.charAt(i);
if(Z[k]==NUM[i]||Z[k]==ch(NUM[i]))
{
X[k]++;
}
}
}
System.out.println("这篇文章中英文字母个数分别为:");
double sum=0;
System.out.println("////////////排序如下:");
for(i=0;i<25;i++)
for(int k=0;k<25-i;k++)
{
if(X[k]<X[k+1])
{
int temp2=X[k];
X[k]=X[k+1];
X[k+1]=temp2;
char temp3=Z[k];
Z[k]=Z[k+1];
Z[k+1]=temp3;
}
}
for(i=0;i<26;i++)
{
System.out.println(Z[i]+"字母个数为:"+X[i]);
sum=sum+X[i];
}
for(i=0;i<26;i++)
{
double jkl=(X[i])/sum*100;
System.out.println(Z[i]+"字母频率为:"+df.format(jkl)+"%");
}
StringTokenizer st = new StringTokenizer(sb.toString(),",.! \n");
String []a1=StatList(sb.toString());
int[]b1=StatList1(sb.toString());
System.out.println("//////////////////////////////");
for(i=0;i<a1.length-1;i++)
for(int j=0;j<a1.length-1-i;j++)
{
if(b1[j]<b1[j+1])
{
int temp6=b1[j];
b1[j]=b1[j+1];
b1[j+1]=temp6;
String temp7=a1[j];
a1[j]=a1[j+1];
a1[j+1]=temp7;
}
}
for(i=0;i<a1.length-1;i++)
{
System.out.println("单词:"+a1[i]+" 且出现的次数:"+b1[i]);
}
}
static char ch(char c)
{
if(!(c>=97&&c<=122))
c+=32;
return c;
}
static String[] StatList(String str) {
StringBuffer sb = new StringBuffer();
HashMap<String ,Integer> has = new HashMap<String ,Integer> (); // 打开一个哈希表
String[] slist = str.split("\\W+");
int sum=0;
int sum1=0;
for (int i = 0; i < slist.length; i++) {
if (!has.containsKey(slist[i])) { // 若尚无此单词
has.put(slist[i], 1);
sum++;
sum1++;
} else {//如果有，就在将次数加1
Integer nCounts = has.get(slist[i]);

has.put(slist[i],nCounts+1 );
}
}
int temp=0;
int temp1=0;
String []a=new String[sum];
int []b=new int[sum1];
Iterator iterator = has.keySet().iterator();
while(iterator.hasNext()){
String word = (String) iterator.next();
a[temp]=word;
temp++;
}
return a;
}
static int[] StatList1(String str) {
StringBuffer sb = new StringBuffer();
HashMap<String ,Integer> has = new HashMap<String ,Integer> (); // 打开一个哈希表
String[] slist = str.split("\\W+");
int sum=0;
int sum1=0;
for (int i = 0; i < slist.length; i++) {
if (!has.containsKey(slist[i])) { // 若尚无此单词
has.put(slist[i], 1);
sum++;
sum1++;
} else {//如果有，就在将次数加1
Integer nCounts = has.get(slist[i]);

has.put(slist[i],nCounts+1 );

}
}
int temp=0;
int temp1=0;
String []a=new String[sum];
int []b=new int[sum1];
Iterator iterator = has.keySet().iterator();
while(iterator.hasNext()){
String word = (String) iterator.next();
b[temp1]=has.get(word);
temp1++;
}
return b;
}
}