Java常用类——基本类型包装类 Character 类

1、概述

• Character 类在对象中包装一个基本类型 char 的值
• Character 类提供了一些确定字符类别的方法，或者将字符大写转换成小写

2、构造方法

• public Character(char value)

package leixing;

public class CharacterDemo {
    public static void main(String[] args){
        Character c1 = new Character((char)97);
        Character c2 = new Character('a');
        System.out.println(c1);//输出a
        System.out.println(c2);//输出a
    }
}

3、成员方法

• public static boolean isUpperCase(char ch)
• public static boolean isLowerCase(char ch)
• public static boolean isDigit(char ch)
• public static char toUpperCase(char ch)
• public static char toLowerCase(char ch)

package leixing;

public class CharacterDemo {
    public static void main(String[] args){
        System.out.println("是不是大写："+Character.isUpperCase('A'));
        System.out.println("是不是大写："+Character.isUpperCase('a'));
        System.out.println("是不是大写："+Character.isUpperCase('0'));
        System.out.println("---------------------------");

        System.out.println("是不是小写："+Character.isLowerCase('A'));
        System.out.println("是不是小写："+Character.isLowerCase('a'));
        System.out.println("是不是小写："+Character.isLowerCase('0'));
        System.out.println("================================");

        System.out.println("是不是数字："+Character.isDigit('A'));
        System.out.println("是不是数字："+Character.isDigit('a'));
        System.out.println("是不是数字："+Character.isDigit('0'));
        System.out.println("++++++++++++++++++++++++++++++++");

        System.out.println("转换成大写："+Character.toUpperCase('a'));
        System.out.println("转换成大写："+Character.toUpperCase('A'));
        System.out.println("-=-=-=-=-=-=-=-=-=-=-=-=-=-=");

        System.out.println("转换成小写："+Character.toLowerCase('a'));
        System.out.println("转换成小写："+Character.toLowerCase('A'));
    }
}

4、案例

• 统计一个字符串中大写字母字符，小写字母字符，数字字符出现的次数。(不考虑其他字符)

package leixing;

import java.util.Scanner;

public class CharacterDemo {
    public static void main(String[] args){
        int bigCount = 0;
        int smallCount = 0;
        int numberCount = 0;

        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个字符串：");
        String s = sc.nextLine();

        char[] c = s.toCharArray();//把字符串转换成字符数组
        for (int i = 0; i < s.length(); i++){//遍历字符数组中的每一个字符
            char cha = c[i];
            if (Character.isUpperCase(cha)){
                bigCount++;
            }else if(Character.isLowerCase(cha)){
                smallCount++;
            }else if(Character.isDigit(cha)){
                numberCount++;
            }
        }
        System.out.println("大写字母有："+bigCount+"个");
        System.out.println("小写字母有："+smallCount+"个");
        System.out.println("数字有："+numberCount+"个");
    }
}