字母大小写互相转换

    public static void main(String[] args) {
    //输入一个或者多个字母
        System.out.println(interconversion("ADASDsadadSS"));
        System.out.println(capital("asada"));
        System.out.println(lower("ASDSAI"));
    }
    public static String tostring(char [] chars){
        String str= "";
        for (int i = 0; i < chars.length; i++) {
            str+=chars[i];
        }
        return str;
    }

    public static String interconversion(String str) {//互相转换
        char [] chars =  str.toCharArray();

        for (int i = 0; i < chars.length; i++) {
            if (chars[i]<97){
                chars[i]=(char) ((int)chars[i]+32);
            }else{
                chars[i]=(char) ((int)chars[i]-32);
            }
        }
       return tostring(chars);
    }

public static String  capital(String str){//全部转为大写
    char [] chars =  str.toCharArray();

    for (int i = 0; i < chars.length; i++) {
        if (chars[i]>=97){
            chars[i]=(char) ((int)chars[i]-32);
        }
    }
return tostring(chars);
}
public static String  lower(String str){//全部转为小写
    char [] chars =  str.toCharArray();
    for (int i = 0; i < chars.length; i++) {
        if (chars[i]<97){
            chars[i]=(char) ((int)chars[i]+32);
        }
    }
    return tostring(chars);
}