What does the following statement sequence print? String str = "Java"; str += " is powerful"; System.out.println(str);

The sequence of statements constructs and modifies a string in Java. Initially, the string variable str is assigned the value "Java". When the second statement str += " is powerful"; is executed, it concatenates the existing value of str ("Java") with the new string (" is powerful"). This results in str being updated to "Java is powerful".

Finally, the System.out.println(str); statement outputs the current value of str, which now holds the complete string "Java is powerful". The output reflects this concatenation process, resulting in the printed output.

Understanding string concatenation and how string variables are updated in Java is crucial, as it demonstrates how operations can modify the state of a variable, which is a foundational concept in programming.