Tag: java

Questions Related to java

public class CreditCard {
 private String cardID;
 private Integer limit;
 public String ownerName;
 public void setCardInformation(String cardID, String ownerName, Integer limit) {
  this.cardID = cardID;
  this.ownerName = ownerName;
  this.limit = limit;
 }
}

Which statement is true?

java

  1. The class is fully encapsulated

  2. The code demonstrates polymorphism

  3. The ownerName variable breaks encapsulation

  4. The cardID and limit variables break polymorphism

Show answer
Correct Option: C 
int x = 12;
while (x < 10) {
    x--;  
}  
System.out.print(x);

What is the result?

java

  1. 0

  2. 10

  3. 12

  4. print statement never be executed

Show answer
Correct Option: C
Explanation:

To solve this question, the user needs to know about while loop and comparison operators.

In the given code snippet, the while loop will only execute if the condition inside the parentheses is true. The code initializes the variable x to 12 and checks if it is less than 10. Since 12 is greater than 10, the condition is false, and the code inside the while loop will never execute. The print statement will execute outside of the loop, which will output the value of the variable x.

Options A, B, and C can be eliminated since none of them represent the correct value.

Option D is incorrect because the print statement will execute regardless of whether the while loop is executed or not.

Therefore, the correct answer is:

The Answer is: C. 12

System.out.format("Pi is approximately %d.", Math.PI); What is the result?

java

  1. Compilation fails

  2. Pi is approximately 3

  3. Pi is approximately 3.141593

  4. An exception is thrown at runtime

Show answer
Correct Option: D

AI Explanation

To answer this question, let's analyze the given code:

System.out.format("Pi is approximately %d.", Math.PI);

The System.out.format method is used to format and print a formatted string to the console. In this case, the string being printed is "Pi is approximately %d.".

The %d is a format specifier that is used for printing integers. However, Math.PI is a double value, not an integer.

Therefore, when this code is executed, it will throw a java.util.IllegalFormatConversionException at runtime because the format specifier %d is not compatible with the Math.PI value.

Hence, the correct answer is D) An exception is thrown at runtime.

NumberFormat nf = NumberFormat.getInstance(); nf.setMaximumFractionDigits(4);
nf.setMinimumFractionDigits(2);  
String a = nf.format(3.1415926);
String b = nf.format(2);

Which statement is true about the result?

java

  1. The value of b is 2

  2. The value of b is 2.00

  3. The value of a is 3.1415

  4. The value of a is 3.141

Show answer
Correct Option: B

AI Explanation

To answer this question, let's go through each statement and evaluate whether it is true or false:

Option A) The value of b is 2 - This statement is false. The NumberFormat object nf is set to format the numbers with a minimum of 2 decimal places. Therefore, the value of b will have 2 decimal places.

Option B) The value of b is 2.00 - This statement is true. The NumberFormat object nf is set to format the numbers with a minimum of 2 decimal places. When the value 2 is formatted using this NumberFormat object, it will be displayed with 2 decimal places, resulting in the value "2.00".

Option C) The value of a is 3.1415 - This statement is false. The NumberFormat object nf is set to format the numbers with a maximum of 4 decimal places. Therefore, the value of a will be rounded to 4 decimal places.

Option D) The value of a is 3.141 - This statement is false. The NumberFormat object nf is set to format the numbers with a minimum of 2 decimal places. Therefore, the value of a will have 2 decimal places.

The correct answer is Option B. The value of b is "2.00" because the NumberFormat object nf is set to format the numbers with a minimum of 2 decimal places.

public class Yippee2 {
  static public void main(String [] yahoo) {
  for(int x = 1; x < yahoo.length; x++) {
  System.out.print(yahoo[x] + " ");
  }
 }
}

and the command line invocation: java Yippee2 a b c What is the result?

java

  1. a b

  2. b c

  3. a b c

  4. Compilation fails

Show answer
Correct Option: B

AI Explanation

To determine the result of the given code and command line invocation, let's go through each option:

Option A) a b - This option is incorrect because it does not include the last element c.

Option B) b c - This option is correct because the code prints the elements starting from index 1 (yahoo[1]) to the last index (yahoo.length - 1). In this case, yahoo[1] is b and yahoo[2] is c. Therefore, the output will be b c.

Option C) a b c - This option is incorrect because it includes the first element a, which is not printed by the code.

Option D) Compilation fails - This option is incorrect because the code does not have any compilation errors. It is a valid Java code.

The correct answer is B. The code will output b c.

public static void main(String[] args) {
  String str = "null"; 
 if (str == null) {
  System.out.println("null");
  } else (str.length() == 0) {
  System.out.println("zero");
  } else {
  System.out.println("some");
  }  
}

What is the result?

java

  1. null

  2. zero

  3. some

  4. Compilation fails

Show answer
Correct Option: D
Explanation:

To solve this question, the user needs to know that the given code is testing whether a string value is null or empty. They also need to know the syntax of if-else statements in Java.

Now, let's go through each option and explain why it is right or wrong:

A. null: This option is incorrect because the code checks if the string is null using the expression str == null, which evaluates to false since str is "null" (a non-null string literal).

B. zero: This option is incorrect because the code does not check if the string is empty using the expression str.length() == 0. Instead, it tries to use an invalid syntax by placing an else block after the if block. This leads to a compilation error.

C. some: This option is incorrect because the code won't reach this block due to the compilation error mentioned above.

D. Compilation fails: This option is correct. The code will fail to compile due to the invalid syntax in the else block. The correct syntax for an if-else statement is:

if (condition) {
    // code block for true case
} else {
    // code block for false case
}

Therefore, the correct code should be:

public static void main(String[] args) {
  String str = "null"; 
  if (str == null) {
    System.out.println("null");
  } else if (str.length() == 0) {
    System.out.println("zero");
  } else {
    System.out.println("some");
  }  
}

The Answer is: D

String[] elements = { "for", "tea", "too" }; 
String first = (elements.length > 0) ? elements[0] : null;

What is the result?

java

  1. Compilation fails

  2. An exception is thrown at runtime

  3. The variable first is set to null

  4. The variable first is set to elements[0]

Show answer
Correct Option: D 
int x = 12;  
while (x < 10) {  
   x--;  
}  
System.out.print(x);

What is the result?
java

  1. 0

  2. 10

  3. 12

  4. print statement never be executed

Show answer
Correct Option: C

After the declaration: char[] c = new char[100]; what is the value of c[50]?

technology java

  1. 50

  2. ‘\u0000'

  3. cannot be determined

  4. always null until a value is

Show answer
Correct Option: B
Explanation:

To answer this question, you need to understand how arrays work in Java. Specifically, the behavior of character arrays when they are initialized.

In Java, when you create an array, all elements in the array are automatically initialized to their default values. For the char data type, the default value is the null character, represented as '\u0000'.

Let's go through each option to understand why it is correct or incorrect:

Option A) 50 - This option is incorrect. When an array of char type is created in Java, its elements are not automatically initialized to their indices. Therefore, c[50] is not equal to 50.

Option B) ‘\u0000' - This option is correct. As mentioned above, when a char array is created in Java, its elements are automatically initialized to the null character, '\u0000'. Therefore, c[50] is equal to '\u0000'.

Option C) cannot be determined - This option is incorrect. In Java, the behavior of array initialization is well-defined. For a char array, all elements are automatically initialized to '\u0000'. Therefore, the value of c[50] can be determined.

Option D) always null until a value is - This option is incorrect. In the context of Java, "null" usually refers to a reference that does not point to any object. But for primitive types, such as char, the concept of "null" does not apply. The default value for a char is '\u0000', not "null".

The correct answer is B) ‘\u0000'. This option is correct because in Java, when a char array is initialized, all of its elements are automatically set to the null character, '\u0000'.