Java 遍历 String 字符串所有字符的操作

package com.app.main.utils;
 
/**
 * Created with IDEA
 * author:Dingsheng Huang
 * Date:2019/6/28
 * Time:下午8:48
 */
public class StringUtils {
 
 public static void main(String[] args) {
 
  String test = "abc123";
  // 遍历所有字符
  for (int i = 0; i < test.length(); i++) {
   char item = test.charAt(i);
   System.out.println(String.valueOf(item));
  }
 }
}

String str = "asdfghjkl";
for(int i=0;i<str.length();i++){
char ch = str.charAt(i);
}

char[] c=s.toCharArray();
for(char cc:c){
 ...//cc直接用了
} 

for(int i=0;i<str.length();i++){
 String subStr = str.substring(i, i+1)
}