Java String Length Examples

Mar 03, 2015 Core Java, Examples, Snippet, String comments

This post will show how to get the length of a Java String. The length of a Java String is the number of characters present in the String. Example Java codes will also be shared below.

String.length()

The Java String class has a method that returns the length of it's instance.

Syntax

Here is the syntax of the method:

public int length()

Note that there is no parameter and that the method is not static. This means that the method can only be invoked through a Java String instance.

The return value of the method is an int that represents the number of characters the String contains.

Example

Here is an example Java class that reads an input from the command line and displays the length of the given string.

public class Test {
   public static void main(String[] args) {
      System.out.print("Please enter a string: ");
      String stringInput = System.console().readLine();
      int stringLength = stringInput.length();
      System.out.println("The number of characters is: " + stringLength);
   }
}

Here is an example run of the program:

Please enter a string: testing123
The number of characters is: 10

More Samples

Here are more examples on how to use Java String Length.

Display each character of a String per line

This sample will read an input String and use the String length to loop through all it's characters.

public class Test {
   public static void main(String[] args) {
      System.out.print("Please enter a string: ");
      String stringInput = System.console().readLine();
      int stringLength = stringInput.length();
      for (int charIndex = 0; charIndex < stringLength; charIndex++) {
         char c = stringInput.charAt(charIndex);
         System.out.println(c);
      }
   }
}

Here is a sample run of the program:

Please enter a string: testing
t
e
s
t
i
n
g

Compare length of two Strings

This example will read two input String from the user. The length o f the two strings will be compared to show which is longer.

public class Test {
   public static void main(String[] args) {
      System.out.print("Please enter first string: ");
      String firstString = System.console().readLine();
      System.out.print("Please enter second string: ");
      String secondString = System.console().readLine();
      //
      int firstStringLength = firstString.length();
      int secondStringLength = secondString.length();
      if (firstStringLength > secondStringLength) {
         System.out.println("The first string is longther than the second string");
      } else if (secondStringLength > firstStringLength) {
         System.out.println("The second string is longther than the first string");
      } else {
         System.out.println("The first and second string have equal lengths");
      }
   }
}

Here are sample runs of the program:

Please enter first string: abc
Please enter second string: defg
The second string is longther than the first string

Please enter first string: apple
Please enter second string: cider
The first and second string have equal lengths

String length validation

The length can also be used to validate that the given string should not exceed some limit.

public class Test {
   public static void main(String[] args) {
      System.out.print("Please enter a string: ");
      String stringInput = System.console().readLine();
      int stringLength = stringInput.length();
      if (stringLength > 10) {
         System.out.println("Input string should not exceed 10 characters");
      } else {
         System.out.println("The input string is valid.");
      }
   }
}

Here are sample runs of the program:

Please enter a string: thequickbrown
Input string should not exceed 10 characters

Please enter a string: apple
The input string is valid.

Do not accept empty String

This example will keep on reading for user input until the user enters a non empty String.

public class Test {
   public static void main(String[] args) {
      String stringInput = "";
      while (stringInput.length() == 0) {
         System.out.print("Please enter a string: ");
         stringInput = System.console().readLine();
      }
      System.out.println("You entered the string: " + stringInput);
   }
}

Here is a sample run of the program:

Please enter a string: 
Please enter a string: 
Please enter a string: 
Please enter a string: test
You entered the string: test