Reading File To String With Stdin Redirection?

I'm working on a project in which I need to read an entire block of text from a file, modify the text, and store the text into a character array. This wouldn't seem so bad, except I have to do this through the command line.

For example, in the terminal:

java program < input.txt

runs the program and uses data from input.txt.

I've considered using an input stream, but most tutorials on reading from a file involve creating a file object such as

FileInputStream fis = new FileInputStream("input.txt");

I'm not supposed to include the file name in the code. I'm not supposed to ask for the file name either.

I've used code such as

final static int MAX = 10000;
public static void main(String[] args) throws IOException {
// TODO code application logic here
InputStreamReader stdin = new InputStreamReader(System.in);
char[] cbuf = new char[MAX];
stdin.read(cbuf);
String str = cbuf.toString();
System.out.println(str);
}

This does store the text into an array, but I need to make adjustments to the text. Using toString prints a memory address.

storing data from an input stream into a string or an array using redirection so that I can then modify the contents of the string/array later on in the program?