Chapter FOUR
Working with Data

Answers

1. The correct answer is C.

Explanation:

• A) A double can be directly assigned to a float without casting.
  • This option is incorrect. A double cannot be directly assigned to a float without casting because double has a larger range and precision than a float.
• B) A boolean can be cast to an int.
  • This option is incorrect. boolean values cannot be cast to int in Java. They are not compatible types.
• C) A String can be assigned to an Object reference variable.
  • This option is correct. A String is an instance of the Object class, and hence it can be assigned to an Object reference variable.
• D) A char is a reference data type.
  • This option is incorrect. char is a primitive data type, not a reference data type.
• E) An int can store a long value without any explicit casting.
  • This option is incorrect. an int cannot store a long value without explicit casting because long has a larger range than int.

2. The correct answer is A.

Explanation:

Let’s break down the expression a + b * c / a - b step-by-step according to the order of operations:

1. Multiplication and Division are performed first from left to right:
   • b * c = 10 * 15 = 150
   • 150 / a = 150 / 5 = 30
2. Addition and Subtraction are performed next from left to right:
   • a + 30 = 5 + 30 = 35
   • 35 - b = 35 - 10 = 25

So, the value of result is 25, and the program prints 25.

• A) 25
  • This option is correct.
• B) 35
  • This option is incorrect.
• C) 20
  • This option is incorrect.
• D) 15
  • This option is incorrect.

3. The correct answer is D.

Explanation:

• A) StringBuilder objects are immutable.
  • This option is incorrect. StringBuilder objects are mutable, meaning they can be changed after they are created.
• B) String objects can be modified after they are created.
  • This option is incorrect. String objects are immutable, meaning once a String object is created, it cannot be modified. Any modification results in a new String object.
• C) StringBuilder is synchronized and thread-safe.
  • This option is incorrect. StringBuilder is not synchronized and is not thread-safe. If synchronization is required, StringBuffer should be used instead.
• D) StringBuilder provides methods for mutable sequence of characters.
  • This option is correct. StringBuilder provides methods for a mutable sequence of characters, allowing for modification of the object without creating new instances.
• E) String and StringBuilder have the same performance characteristics for string manipulation.
  • This option is incorrect. String and StringBuilder do not have the same performance characteristics for string manipulation. StringBuilder is generally more efficient for such operations because it is mutable and does not create new instances with each modification.

4. The correct answers are A and B.

Explanation:

• A) Text blocks can span multiple lines without needing escape sequences for new lines.
  • This option is correct. Text blocks can indeed span multiple lines without needing escape sequences for new lines, making it easier to work with multi-line strings.
• B) Text blocks preserve the exact format, including whitespace, of the code as written.
  • This option is correct. Text blocks preserve the exact format, including whitespace, of the code as written. This is useful for maintaining the original layout of the text.
• C) Text blocks can only be used within methods.
  • This option is incorrect. Text blocks can be used anywhere a regular String can be used, not just within methods. They can be part of class fields, method parameters, etc.
• D) Text blocks automatically trim leading and trailing whitespace from each line.
  • This option is incorrect. Text blocks do not automatically trim leading and trailing whitespace from each line. They preserve the exact whitespace as written in the code.
• E) Text blocks require a minimum indentation level of one space.
  • This option is incorrect. Text blocks do not require a minimum indentation level of one space. The leading indentation common to all lines is removed automatically, but lines within the text block can have zero or more leading spaces.

5. The correct answer is D.

Explanation:

• A) The Math.round() method returns a double.
  • This option is incorrect. The Math.round() method returns a long when given a double argument and an int when given a float argument.
• B) The Math.random() method returns a random integer.
  • This option is incorrect. The Math.random() method returns a double value between 0.0 (inclusive) and 1.0 (exclusive).
• C) The Math.max() method can only be used with integers.
  • This option is incorrect. The Math.max() method can be used with various numeric types, including int, long, float, and double.
• D) The Math.pow() method returns the result of raising the first argument to the power of the second argument.
  • This option is correct. The Math.pow() method returns the result of raising the first argument to the power of the second argument. Both arguments are of type double.
• E) The Math.abs() method can only be used with positive numbers.
  • This option is incorrect. The Math.abs() method can be used with negative numbers to return their absolute value, and it works with various numeric types including int, long, float, and double.