Creating a New String by Joining Two Strings

The addition operator can be used to append, or join, two String objects together or append a String object with a primitive value. In order to append a String with a primitive, the compiler will automatically create a String literal out of the primitive value. This is a String Conversion.

It is important to remember that items are added together from left to right. This applies to expressions that involve String literals as well.

Your Turn

Example 1

In all the cases above, we could have assigned the resulting String literal to the variable.

Example 2

Where this is really powerful, is if the primitive values are being stored in a variable of their own.

Example 3

• Modify the code below to use the variable weight in the assignment of message1.

Order of Operations with String Literals and Primitives

• Predict the value that will be assigned to sumMessage.
• Check your thinking by running it in the Java Playground.

Your Turn

Visual Illustration

This visual illustrates the order of operations for this assignment statement.

Your Turn

Let's try this in the Java Playground.

• Predict the value that will be assigned to sumMessage2.
• Check your thinking by running it in the Java Playground.

Explanation:

• The sum of "What is the value of " and 3 is evaluated first, resulting in "What is the value of 3".
• The sum of "What is the value of 3" and " plus " is evaluted second, resulting in "What is the value of 3 plus ".
• The sum of "What is the value of 3 plus " and 5 is evaluated third, resulting in "What is the value of 3 plus 5".
• The sum of "What is the value of 3 plus 5" and ? is evaluated forth, resulting in "What is the value of 3 plus 5? ".
• The sum of "What is the value of 3 plus 5? " and 3 is evaluated fifth, resulting in "What is the value of 3 plus 5? 3".
• The sum of "What is the value of 3 plus 5? 3" and 5 is evaluated sixth, resulting in "What is the value of 3 plus 5? 35".

You can use parenthesis to override the order of operation so to correct this output to be "What is the value of 3 plus 5? 8".

Your Turn

Let's try this in the Java Playground.

• Predict the value that will be assigned to sumMessage3.
• Check your thinking by running it in the Java Playground.

Explanation:

• The sum of 3 and 5 in parenthesis is evaluated first, resulting in 8.
• The sum of "What is the value of " and 3 is evaluated second, resulting in "What is the value of 3".
• The sum of "What is the value of 3" and " plus " is evaluted third, resulting in "What is the value of 3 plus ".
• The sum of "What is the value of 3 plus " and 5 is evaluated forth, resulting in "What is the value of 3 plus 5".
• The sum of "What is the value of 3 plus 5" and ? is evaluated fifth, resulting in "What is the value of 3 plus 5? ".
• The sum of "What is the value of 3 plus 5? " and 8 is evaluated fifth, resulting in "What is the value of 3 plus 5? 8".

Resources

• Practice: Arithmetic Expressions Exploration
• Learn: Declaring Strings
• Learn: Using the String Class

Next Learn Tutorial

Learn: Using Constants in Java