To iterate through each character of a string in Java, you can use a for loop with the charAt() method of the String class. Here's an example:

String str = "Hello, World!";
for (int i = 0; i < str.length(); i++) {
    char c = str.charAt(i);
    System.out.print(c + " ");
}

In the above example, we define a String variable str with the value "Hello, World!". We then use a for loop to iterate through each character of the string.

Inside the loop, we use the charAt() method to get the character at the current index i. We store the character in a char variable c. Finally, we print the character to the console using the System.out.print() method.

After running the above code, the output would be:

H e l l o ,   W o r l d !

This program iterates through each character in the String and prints it to the console. Note that the charAt() method starts at index 0 and goes up to length() - 1.