求解

[XIUALL2020]

随便定义一个字符数组并初始化，要求把字符数组中的大写转小写，小写转大写，
如果遇到数字，则把数字转为对应的负数输出
{'a','B',''',',','9'}

[beyond丿qq:1559810637]

for循环里面用if判断，然后用string转大小写的方法

[mmmdcsmtos]

循环去呗。。。。

[自由自在_Yu]

public static void main(String[] args) {
		String[] str = new String[]{"a","B"," ","9"};
		for (int i = 0; i < str.length; i++) {
			System.out.print(str[i]);
		}
		for (int i = 0; i < str.length; i++) {
			if(Character.isLowerCase(str[i].charAt(0))){
				str[i] = str[i].toUpperCase();
			}else if(Character.isUpperCase(str[i].charAt(0))){
				str[i] = str[i].toLowerCase();
			}else if(Character.isDigit(str[i].charAt(0))){
				str[i] = "-" + str[i];
			}
		}
		System.out.println();
	    for (int i = 0; i < str.length; i++) {
			System.out.print(str[i]);
		}
	}