public static void main(String[] args) {
String str = "keep walking!!!";
//方法一
char[] charArray = str.toCharArray();
for (char i:charArray){
System.out.println(i);
}
// 方法二
for (int i = 0; i < str.length(); i++) {
System.out.println(str.charAt(i));
}
//方法三
for (int i = 0; i < str.length(); i++) {
System.out.println(str.substring(i, i + 1));
}
}