In Java, you can use String.toCharArray() to convert a String into a char array.
StringToCharArray.java
package com.mkyong.utils;
public class StringToCharArray {
    public static void main(String[] args) {
        String password = "password123";
        char[] passwordInCharArray = password.toCharArray();
        for (char temp : passwordInCharArray) {
            System.out.println(temp);
        }
    }
}
Output
p
a
s
s
w
o
r
d
1
2
3
Java 8 – Convert String to Stream Char
For Java 8, you can uses .chars() to get the IntStream, and convert it to Stream Char via .mapToObj
package com.mkyong.utils;
package com.mkyong.pageview;
public class Test {
    public static void main(String[] args) {
        String password = "password123";
        password.chars() //IntStream
                .mapToObj(x -> (char) x)//Stream<Character>
                .forEach(System.out::println);
    }
}
Output
p
a
s
s
w
o
r
d
1
2
3
References
- JavaDoc – toCharArray
- Why is String.chars() a stream of ints in Java 8?