Constructing a String

In the Declaring Strings tutorial, we used String objects, created by using string literals. Reminder that a string literal is characters enclosed in double quotes ("). In Introduction to Arithmetic Expressions, we used the + operator to concatenate, or add, string literals. We also used string literals as part of output in Introduction to Console Input and Output, Formatting Output with Escape Sequences and Formatting Output with Text Blocks.

Need a refresher on creating objects and calling methods? Learn: Creating Objects and Calling Methods

String Constructor

While in previous String tutorials, we used string literals to create String objects. There is a String constructor that can also be used. To satisfy any curiousity, here is an example of how to create a String object using a String constructor:

String myName = new String("Duke");

We will likely stick to using string literals to create String objects.

Strings Are Immutable

Recall that the value of a String is immuntable, it cannot be changed. A String variable's value can be altered by assigning it to a new String, but not by changing the existing String. Consider the example below.

String phrase = "Duke";
phrase = phrase + " loves Java";

The value "Duke" is concatenated with " loves Java" and a new String object is created that is "Duke loves Java".

String Methods

Throughout this series of String tutorials, we have provided some common String methods and examples of their use. For a complete list of String methods can be found in the String API.

Methods that are part of the AP Computer Science A Java subset are denoted by the APCSA label.

int length()

This method returns the number of characters that are in the String.

Your Turn

Let's try it in the Java Playground.

• Predict the value of wordLength.
• Add a statement to compute the length of phrase and assign it to wordLength.
• Predict the new value of wordLength.
• Run the code to check you predictions.

• wordLength is assigned the value 4, since there are 4 characters in Duke.
• phraseLength is assigned the value 15, since there are 13 letters and two spaces in phrase.

Complete List of String Learn Tutorials

• Learn: Declaring Strings
• Learn: Constructing a String
• Learn: String Indexing
• Learn: Comparing Strings with compareTo methods
• Learn: Comparing Strings with equals methods
• Learn: Creating Substrings
• Learn: Using the split Method on a String
• Learn: Creaing a new String with the Case Changed

Resources

• Learn: Declaring Strings
• Learn: Introduction to Arithmetic Expressions
• Learn: Introduction to Console Input and Output
• Learn: Formatting Output with Escape Sequences and Text Blocks
• Practice: Evaluating Expressions that Use String Methods
• Practice: Write Code that Uses the String Methods
• Practice: AP Computer Science A String Free Response Questions

Next Learn Tutorial

Learn: String Indexing