1、问题

统计一个字符串中的字母，数字，空格（含多种）和其它类型字符的数量；

2、解答

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 三种方式实现统计字符串中的字符，数字，空格和其它字符个数
 * 
 */
public class CharCountStringTest {
    public static void main(String[] args) {
        String s= "123abc-\t\nd n";

        //根据字符统计
        getCharKindByChar(s);

        //根据ASCLL码统计
        getCharKindByASCLLCode(s);

        //根据正则统计
        getCharKindByRegex();


    }


    //1、根据字符统计
    private static void getCharKindByChar(String s){
        int charCount=0,numberCout=0,blankCount=0,otherCount=0;
        for (int i=0;i<s.length();i++){
            //英文字母
            char temp=s.charAt(i);
            if (('a'<=temp&& temp<='z')||('A'<=temp&&temp<='Z')){
                charCount++;
                //数字类型
            }else if('0'<=temp&&temp<='9'){
                numberCout++;
                //空格类型(不全)
            }else if(temp=='\t'||temp=='\n'||temp==' '){
                blankCount++;
                //其它类型
            }else {
                otherCount++;
            }
        }
        System.out.println("**********");
        System.out.println("英文字母出现的次数："+charCount);
        System.out.println("数字出现的次数："+numberCout);
        System.out.println("空格字符出现的次数："+blankCount);
        System.out.println("其它字符："+otherCount);
    }

    //2、根据ASCLL码统计
    private static void getCharKindByASCLLCode(String s){
        int charCount=0,numberCout=0,blankCount=0,otherCount=0;
        for (int i=0;i<s.length();i++){
            //英文字母
            char temp=s.charAt(i);
            if ((65<=temp&& temp<=90)||(97<=temp&&temp<=122)){
                charCount++;
                //数字类型
            }else if(48<=temp&&temp<=57){
                numberCout++;
                //空格类型
            }else if(temp<=32){
                blankCount++;
                //其它类型
            }else {
                otherCount++;
            }
        }
        System.out.println("**********");
        System.out.println("英文字母出现的次数："+charCount);
        System.out.println("数字出现的次数："+numberCout);
        System.out.println("空格字符出现的次数："+blankCount);
        System.out.println("其它字符："+otherCount);
    }

    //3、根据正则表达式匹配
    private static void getCharKindByRegex(){
        InputStreamReader inputStreamReader = new InputStreamReader(System.in);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        System.out.println("请输入字符串：");
        String string="";

        try {
            string=bufferedReader.readLine();
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        Pattern letterPattern = Pattern.compile("[a-zA-Z]");
        Pattern numberPattern = Pattern.compile("[0-9]");
        Pattern blandPattern = Pattern.compile("[\\s|\r|\n|\t]");//不全

        Matcher letterMatcher = letterPattern.matcher(string);
        Matcher numberMatcher = numberPattern.matcher(string);
        Matcher blandMatcher = blandPattern.matcher(string);

        StringBuffer stringBufferLetter = new StringBuffer();
        StringBuffer stringBufferNumber = new StringBuffer();
        StringBuffer stringBufferBlank = new StringBuffer();

        while(letterMatcher.find()){
            stringBufferLetter.append(letterMatcher.group(0));
        }
        while(numberMatcher.find()){
            stringBufferNumber.append(numberMatcher.group(0));
        }
        while(blandMatcher.find()){
            stringBufferBlank.append(blandMatcher.group(0));
        }

        int otherNumber=string.length()-stringBufferLetter.length()-stringBufferNumber.length()-stringBufferBlank.length();

        System.out.println("**********");
        System.out.println("字母类型："+ stringBufferLetter.length()+"个");
        System.out.println("数字类型："+ stringBufferNumber.length()+"个");
        System.out.println("空格类型："+ stringBufferBlank.length()+"个");
        System.out.println("其它类型："+ otherNumber+"个");


    }


}