Mutual conversion of Java array and string

Convert string to array

String str = "123abc";
char[] arr = str.tocharArray();    // char数组
for (int i = 0; i < arr.length; i++) {
    System.out.println(arr[i]);    // 输出1 2 3 a b c
}

String str = "123abc";
String[] arr = str.split("");
for (int i = 0; i < arr.length; i++) { // String数组
    System.out.print(arr[i]); // 输出 1 2 3 a b c
}

String str = "123abc" ; byte [] arr = str.getBytes();

StringUtils.join(null) = null;
StringUtils.join([]) = "";
StringUtils.join([null])= "";
StringUtils.join(["a","b","c"]) = "abc";
StringUtils.join([null,"","a"]) = "a";
String[] str = { "1","2","a","b" };
// 将数组变成字符串
StringUtils.join(str);
// 将数组用逗号分隔变成字符串
StringUtils.join(str,",");

Convert array to string

char[] arr = { 'a','b','c' };
String string = String.copyValueOf(arr);
System.out.println(string); // 输出abc

String[] arr = { "123","abc" };
StringBuffer sb = new StringBuffer();
for (int i = 0; i < arr.length; i++) {
    sb.append(arr[i]); // String并不拥有append方法，所以借助 StringBuffer
}
String sb1 = sb.toString();
System.out.println(sb1); // 输出123abc