Determine the Length of a Text String in a Java Program
By Stephen Bucaro
In computer programming, a letter or digit is called a character and a collection of letters
or digits that make a phrase, sentence, or paragraph, is called a string. Java uses the
.length method to return the length, in characters, of the text contained in a String object.
Shown below is the Java code to determine the length of the string "How long is this text?".
public class lengthofText
public static void main(String s)
JFrame frame = new JFrame();
frame.setTitle("Length of Text");
String testText = "How long is this text?";
int testLen = testText.length();
String result = "The string is " + testLen + " characters long.";
JTextArea myText = new JTextArea();
I generally hate it when people add a bunch of extra code to an example. It confuses things.
But in this case I've included the javax.swing library and added code to create a
JFrame and a JTextArea. If I didn't add this extra code, you would need to use
the System.out.print command to output text, and I don't think that's an interesting
or realistic way to learn Java programming.
In this example, these lines create a String object named testTextand initializes it with
the text "How long is this text?". Then the String object's .length method is used to
return the length of the string and store it in the integer variable testLen. Then the
concatenate operator (+) is used to create the output message and store it in a
String object named result.
Finally, the line myText.append(result); is used to place the output message in the
JTextArea object for display in the program's window.
Note that, although in Java, the names of primitive variable types, like int and char
begin with lower-case letters, the String variable type is capitalized. That's because strings
are actually objects, which makes them very powerful because they contain methods like
.length() and getChars.
If you're a beginner, for this example, I recommend downloading and installing the Java Development Kit from
Oracle's web site.
Type the code into a text file using a basic text editor like Window's Notepad (Do not use a word processor
because they insert formatting codes into the file), saving the file with the .java file extension. Then
use a batch file to compile the program. The batch file needs to contain the path to the compiler and the
path to the source file, an example of compile.bat is shown below.
c:\Program Files\java\jdk1.8.0_121\bin\javac c:\Users\Stephen\Desktop\program_name.java
The pause command on the second line will cause the DOS shell to stay open until you press any key,
allowing you to read any errors. If successful, the compiler will create an executable file with the
.class file extension. Then use a batch file to run the program. The batch file needs to contain
the start command, the name of the java program launcher, and the name of the compiled java class
file (without the .class extension). An example of run.bat is shown below.
start javaw program_name
The javaw launcher displays the result of your program, or error information if it fails, in a window.