Java Processing a String One Character at a Time

Java Processing a String One Character at a Time

Problem 

You want to process the contents of a string, one character at a time. 

Solution 

Use a for loop and the String’s charAt( ) method. 

Explained

A string’s charAt( ) method retrieves a given character by index number (starting at zero) from within the String object. To process all the characters in a String, one after another, use a for loop ranging from zero to String.length( )–1. Here we process all the characters in a String:

// StrCharAt.java
String a = "A quick bronze fox leapt a lazy bovine";
for (int i=0; i < a.length( ); i++)
 System.out.println("Char " + i + " is " + a.charAt(i));

A checksum is a numeric quantity representing and confirming the contents of a file. If you transmit the checksum of a file separately from the contents, a recipient can checksum the file—assuming the algorithm is known—and verify that the file was received intact. Example 3-3 shows the simplest possible checksum, computed just by adding the numeric values of each character. Note that on files, it does not include the values of the newline characters; to fix this, retrieve System. getProperty("line.separator"); and add its character value(s) into the sum at the end of each line. Or give up on line mode and read the file a character at a time.

/** CheckSum one file, given an open BufferedReader. */
 public int process(BufferedReader is) {
 int sum = 0;
 try {
 String inputLine;
 while ((inputLine = is.readLine( )) != null) {
 int i;
 for (i=0; i<inputLine.length( ); i++) {
 sum += inputLine.charAt(i);
 }
 }
is.close( );
 } catch (IOException e) {
 System.out.println("IOException: " + e);
 } f
 return sum;
}