A string to char array is as simple as
String str = "someString";
char[] charArray = str.toCharArray();
Can you explain a little more on what you are trying to do?
* Update *
if I am understanding your new comment, you can use a byte array and example is provided.
byte[] bytes = ByteBuffer.allocate(4).putInt(1695609641).array();
for (byte b : bytes) {
System.out.format("0x%x ", b);
}
With the following output
0x65 0x10 0xf3 0x29