Coding 4 All 2023 Java Final

In order to compare int, float and double variables, you can use <, >, ==, !=, <=, >=, but to compare char and String variables, you must use compareTo(), equals()and equalsIgnoreCase().

• True

• False

Answer explanation

In order to compare int, float and double variables, you can use <, >, ==, !=, <=, >=, but to compare char and String variables, you must use compareTo(), equals()and equalsIgnoreCase().

Assume that boolean done = false, int x = 10, int y = 11, String s = "Help" and String t = "Goodbye". Then the expression (!done && x <= y) is true. 

• True

• False

Answer explanation

Since done is false, !done is true.  Since 10 < 11, x <= y is true.  Therefore, the entire expression is true. 

Assume that boolean done = false, int x = 10, int y = 11, String s = "Help" and String t = "Goodbye". Then the expression (s.concat(t).length() < y) is true. 

• True

• False

Answer explanation

Concatenating s and t gives a String that is 11 characters long and 11 < 11 is false. 

f you create an ArrayList without specifying the type of element, the ArrayList will store Object references which means you can put any type of object in the list. 

 

• True

• False

Which of the sets of statements below will add 1 to x if x is positive and subtract 1 from x if x is negative but leave x alone if x is 0? 

• if (x > 0) x++; 

  else x--;  

• if (x > 0) x++; 

  else if (x < 0) x--;  

• if (x > 0) x++; 

  if (x < 0) x--; 

• if (x == 0) x = 0; 

  else x++; 

  x--;  

Answer explanation

In B, if x is positive, x++ is performed, else if x is negative x-- is performed and otherwise, nothing happens, or x is unaffected.  In A, C, D and E, the logic is incorrect.  In A, x-- is done if x is not positive, thus if x is 0, x becomes -1 which is the wrong answer.  In C, if x is positive, then x++ is performed.  In either case, the next statement is executed and if x is not negative, the else clause is performed setting x to 0.  So if x is positive, it becomes 0 after this set of code.  In D, x++ and x-- are both performed if x is not 0.  And in E, this code does not attempt to determine if x is positive or negative, it just adds one and then subtracts one from x, leaving x where it started. 

Consider the following code that will assign a letter grade of 'A', 'B', 'C', 'D', or 'F' depending on a student's test score. 

if (score >= 90) grade = 'A'; 

if (score >= 80) grade = 'B'; 

if (score >= 70) grade = 'C'; 

if (score >= 60) grade = 'D'; 

else grade = 'F';  

• This code will work correctly in all cases. 

• This code will work correctly only if the grade is greater than or equal to 60.

• This code will work correctly only if the grade is less than 60. 

• This code will work correctly only if the grade is less than 70. 

• This code will not work correctly under any circumstances. 

Answer explanation

The problem with this code is that it consists of three if statements followed by one if-else statement, rather than a nested if-else statement.  So the logic is improper.  If the student's grade falls into the 'A' category, then all 4 conditions are true and the student winds up with a 'D'.  If the student's grade falls into the 'B' category, then the first condition is false, but the next three are true and the student winds up with a 'D'.  If the student's grade falls into the 'D' category, then the only condition that is true is the one that tests for 'D' and so the grade is assigned correctly.  If the student's grade falls into the 'F' category, then none of the conditions are true and an 'F' is assigned correctly.  So, only if the grade is less than 70 does the code work correctly. 

What is wrong, logically, with the following code? 

if (x > 10)  

   System.out.println("Large"); 

   else if (x > 6 && x <= 10) 

      System.out.println("Medium"); 

      else if (x > 3 && x <= 6) 

          System.out.println("Small"); 

         else  

            System.out.println("Very small");  

• There is no logical error, but there is no need to have x <= 10 in the second conditional or x <= 6 in the third conditional. 

• There is no logical error, but there is no need to have x > 6 in the second conditional or x > 3 in the third conditional. 

• The logical error is that no matter what value x is, Very small is always printed out. 

• The logical error is that no matter what value x is, Large is always printed out. 

• There is nothing wrong with the logic at all. 

Answer explanation

Because this is a nested if-else statement, if (x>10)is true, then the first println statement is executed and the rest of the statement is skipped.  If (x>10)is not true, then the first else clause is executed and the next if condition is tested.  At this point, (x>10)is known to be false and therefore (x<=10)must be true, so there is no need to check this inequality.  Similarly, if (x>6)is false, then the second else clause is executed and the third if condition is tested.  However, (x<=6)must be true, so there is no need to check this inequality. 

 

If a break occurs within the innermost loop of a nested loop that is three levels deep

• just the innermost loop will be "broken" 

• all loops are "broken" and execution continues from after the end of the loop 

• all but the outermost loops are "broken" and execution continues from the next iteration of the outermost loop 

• a syntax error is generated unless there are break or continue statements at each loop level 

• None of these are true 

Answer explanation

The innermost loop is broken, and execution continues from just after the end of that loop.

How many times will the following loop iterate? 

int x = 10; 

while (x > 0) 

{ 

   System.out.println(x); 

   x--; 

}  

• 0

• once

• 9 times

• 10 times

• 11 times

Answer explanation

Since the condition is tested before the loop body executes, the loop will not execute once x == 0.  So, the loop iterates for x = 10, x = 9, ..., x = 1, or 10 times. 

What is returned by values.length?

• 0

• 5

• 6

• 7

• 18

Answer explanation

The length operator for an array returns the size of the array. The Code Example shows that that values stores 7 elements and since it is full, the size of values is 7.