包装类_Character

1 构造方法
注意加号有自动提升类型的作用，将char转换为Int

//1 构造方法只有一个，public Character(char value) 

public class TestCharacter {
    public static void main(String[] args) {
        Character ch = new Character('a');
        Character ch2 = new Character((char)100);
        System.out.println(ch);//a
        System.out.println(ch2);//d
        // 加号使char进行了类型转换，转换为int
        System.out.println(ch+ch2);//197
        
    }
}

2 判断字符类型&转换大小写

/*成员方法
* public static boolean isUpperCase(char ch)判断是否为大写字母
*public static boolean isLowerCase(char ch)判断是否为小写字母
*public static boolean isDigit(char ch)判断是否为数字
*public static char toUpperCase(char ch)将字符大写
*public static char toLowerCase(char ch)将字符小写

 * 
 */
public class TestCharater02 {
    public static void main(String[] args) {
        
        System.out.println(Character.isUpperCase('a'));
        System.out.println(Character.isUpperCase('A'));
        System.out.println(Character.isUpperCase('0'));
        System.out.println("-----------------------------");
        
        System.out.println(Character.isLowerCase('a'));
        System.out.println(Character.isLowerCase('A'));
        System.out.println(Character.isLowerCase('0'));
        System.out.println("-----------------------------");
        
        System.out.println(Character.isDigit('a'));
        System.out.println(Character.isDigit('A'));
        System.out.println(Character.isDigit('0'));
        System.out.println("-----------------------------");
        
        System.out.println(Character.toUpperCase('a'));
        System.out.println(Character.toUpperCase('A'));
        System.out.println("-----------------------------");
        
        System.out.println(Character.toLowerCase('a'));
        System.out.println(Character.toLowerCase('A'));
        System.out.println("-----------------------------");
    }
}

3 练习_判断输入的字符串中大小写

/**
 * 统计字符串中大小写字母以及数字的个数
 */
import java.util.Arrays;
import java.util.Scanner;

public class TestCharacter03 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个字符串：");
        String s = sc.nextLine();
        int[] ds = count(s);
        System.out.println("大写，小写，数字的个数为："+Arrays.toString(ds));
        
    }
    public static int[] count(String s){
        int ucount = 0;
        int lcount = 0;
        int dcount = 0;
        char[] chs = s.toCharArray();
        for(int i=0;i<chs.length;i++){
            if(Character.isUpperCase(chs[i])){
                ucount++;
            }else if(Character.isLowerCase(chs[i])){
                lcount++;
            }else if(Character.isDigit(chs[i])){
                dcount++;
            }
        }
        int[] count = {ucount,lcount,dcount};
        return count;
    }
}