CSI midterm

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Which of the following will cause a syntax error?

(10 < num) && (num < 30) This one 10 < num < 20 10 < num && num < 25 num > 10 && num < 40

What is output of the following Java code? int num = 15; while (num > 0) num = num - 3; System.out.println(num);

String sentence; String str1, str2, str3, str4; int length1; sentence = " First exam is on Monday. " ; str1 = sentence.substring(6, 12); str2 = str1.substring(0, 4); str3 = sentence.replace( ' i ' , ' # ' ); str4 = sentence.indexOf( "on" ); length1 = sentence.length(); Based on the code above, what is the value of str4?

What is the output of the following Java code? int x = 57; int y = 3; switch (x % 9) { case 0: case 1: y++; case 2: y = y - 2; break; case 3: y = y + 2; case 4: break; case 5: case 6: y = y + 3; } System.out.println(y);

2, 5, 6, 57 ???

'A' < 'a' && 4 <= 8 || 2.5 >= 7 || 4 < y Based on the code above, which part of the expression is not evaluated?

2.5 >= 7 4 < y this one 2.5 >= 7 || 4 < y 4 <= 8

Suppose that you have the following code: int sum = 0; int num = 8; if (num < 0) sum = sum + num; else if (num > 5) sum = num + 15; After this code executes, what is the value of sum?

What is the value of counter after the following statements execute? counter = 1; while (counter < 30) counter = 2 * counter;

What is the output of the following statement? System.out.printf("%.2f", 48.9);

48.90

1, 1, 2, 3, 5, 8, 13, 21, ... What is the tenth Fibonacci number in the sequence above?

int x, y; if (x < 4) y = 2; else if (x > 4) { if (x > 7) y = 4; else y = 6; } else y = 8; based on the code above, what is the value of y if x = 5?

The expression (int) 8.7 evaluates to ____.

Relational Operators

==, !=, >, <, >=, <=

sentinel controlled loop

A loop that runs until a given condition becomes true.

EOF-controlled while loop

Continues to execute until the program detects the end-of-file marker

which of the following does not have an entry condition?

EOF-controlled while loop sentinel-controlled while loop this one???????? do...while loop for loop

What of the following does not have an entry condition?

EOF-controlled while loop This one? sentinel-controlled while loop do...while loop for loop

True or false: A "break statement is legal in a "while" loop, but not in a "for" loop.

False

True or false: A syntax error will result if the control statements of a for loop are omitted.

False

True or false: EOF-controlled while loop is another name for sentinel-controlled while loop.

False

True or false: Given a decima number, the method format of the class String returns the strong containing the digits of the formatted number.

False

True or false: Given a decimal number, the method format of the class String returns the string containing the digits of the formatted number.

False

True or false: In the for statement, if the logical expression is omitted, it is assumed to be false.

False

True or false: Java automatically initializes all variables.

False

True or false: Suppose console is a Scanner object initialized with the standard input device and feet and inches are int variables. Consider the following statements: feet = console.nextInt(); inches = console.nextInt(); These statements require the value of feet and inches to be input on separate lines.

False

True or false: Suppose console is a Scanner object initialized with the standard input device. The expression console.nextInt(); is used to read one int value and the expression console.nextDouble(); is used to read two int values.

False

True or false: Suppose z = 1834.762. The output of the statement System.out.printf("%.1f", z); is 1834.800.

False

True or false: The expression 'A' <= 'B' evaluates to false while the expression 'A' < 'B' evaulate to true

False

True or false: The operator = and == have the same order of precedence.

False

True or false: int alpha = 7; int beta = console.nextInt(); switch (beta) { case 5: alpha = alpha + 1; case 6: alpha = alpha + 2; case 7: alpha = alpha + 3; default: alpha = alpha + 5; } System.out.print(alpha); The output of this code is 9.

False

True or false: to use the content of the java.lang package in a program, they must be imported using the improt statement.

False

True or false: A computer program will recognize both = and == as the equality operator.

False

True or false: A while loop is a post-test loop.

False

True or false: The statement System.exit(0); is found at the end of every working Java program.

False

True or false: The following for loop executes 21 times. (Assume all variables are properly declared.) for (i = 1; i <= 20; i = i + 1) System.out.println(i);

False, 20 times

True or false: The output of the Java code, assuming that all variables are properly declared, is 32. num = 10; while (num <= 32) num = num + 5; System.out.println(num);

False, 35

True or false: The output of the Java code, assuming that all variables are properly declared, is: 23. num = 10; while (num <= 32) num = num + 5; System.out.print(num)

False, 35

True or false: if a = 4; and b = 3;, then after the statement a = b; executes, the value of b is 4 and the value of a is 3.

False, a and b = 3

True or false: In the class String , the substring method inserts a string into another string.

False, it selects specific parts in a string (1,3)

True or false: Suppose x = 8. After the execution of the statement y = x++; y is 8 and x is 10.

False, y = 9 x = 8

flag controlled loop

Loop where bool variable is used to control how many times the loop executes.

Given char ch; int num; double pay; Which of the following assignment statements are valid? (i) ch = ' * ' ; (ii) pay = num * pay; (iii) rate * 40 = pay;

Only (i) is valid this one (i) and (ii) are valid (ii) and (iii) are valid (i) and (iii) are valid

The standard output object in Java is ____.

System.out

Suppose that x is an int variable. Which of the following expressions always evaluates to false?

This one (x > 0) || (x <= 0) (x > 0) || (x == 0) (x > 0) && ( x <= 0) (x >= 0) && (x == 0)

Which of the following statements would store input in name?

This one name = JOptionPane.showInputDialog("Enter your name and press OK"); name = JOptionPane.showMessageDialog("Enter your name and press OK", JOptionPane.PLAIN_MESSAGE, null); name = System.in(); name = JOptionPane.input("Enter your name and press OK");

Which of the following statemnets would store input in name?

This one? name = JOptionPane.showInputDialog("Enter your name and press OK"); name = JOptionPane.showMessageDialog("Enter your name and press OK", JOptionPane.PLAIN_MESSAGE, null); name = System.in(); name = JOptionPane.input("Enter your name and press OK");

True or false: A counter-controlled loop is used when the exact numbeer of data entries is known

True

True or false: A loop is a control structure that causes certain statements to be executed over and over until certain conditions are met.

True

True or false: A program uses selection to implement a branch

True

True or false: After a break statement executes, the program continues to execute with the first statement after the structure.

True

True or false: Assume that all variables in the following code are properly declared and that the input is 3 7 4 -1. The output is 13. num = console.nextInt(); sum = num; while (num != -1) { num = console.nextInt(); sum = sum + num; } System.out.println(sum);

True

True or false: Both System.out.println and System.out.print can be used to output a string on the standard output device.

True

True or false: Control variables are automatically initialized in a loop.

True

True or false: If "length" denotes the length of a nonnull string, then "length - 1" give the index of the last character in the string.

True

True or false: In Java, !, &&, and || are called logic al operators.

True

True or false: In the case of an infinite while loop, the while expression (that is, the loop condition) is always true.

True

True or false: In the case of the sentinel-controlled while loop. the first item is read before the while loop is entered.

True

True or false: String variables are reference variables.

True

True or false: Suppose P and Q are logical expressions. The expression "P || Q" is true if both P and Q are true.

True

True or false: Suppose that index is an int variable. The statement index = index + 1; is equivalent to index++;

True

True or false: Suppose that name is a String variable. Then the following two statements are equivalent. name = "Danny"; name = new String("Danny");

True

True or false: Suppose x = 18.6. The output of the statement System.out.println((int)(x) / 3); is 6.

True

True or false: The control statements in the for loop include the initial expression, logical expression, and update expression.

True

True or false: The execution of a "break" statement in a "switch" statement terminates the "switch" statement

True

True or false: The expression "!(x <= 0)" is true only if x is a positive number

True

True or false: The loop condition of a "while" loop is reevaluated before every iteration of the loop.

True

True or false: The output of the following Java code is: Stoor. int count = 5; System.out.print("Sto"); do { System.out.print('o'); count--; } while (count >= 5); System.out.println('r');

True

True or false: The pair of characters // is used for single line comments.

True

True or false: The value of a variable may change during progrma execution.

True

True or false: A value such as 'd' is called a character constant.

True

True or false: The null string contains onlly the blank character.

True

True or false: the null string contains only the blank character.

True

True or false; Suppose that index is an int variable. The statement index= index + 1; is equivalent to index++

True

True or false: The class JOptionPane allows a programmer to use graphical interface components to obtain input from a user.

True, JOptionPane.showInputDialog

True or false: To read data from a file of unspecified length, an EOF-controlled while loop is a better choice than a counter-controlled while loop.

True, because EOF is a file reader

True or false: The classes Integer, Float, and Double are called wrapper classes.

True, wrapper classes also include boolean, byte, character, long, and short

If str1 is "Hello" and str2 is "Hi", which of the following could not be a result of str1.compareTo(str2);?

Which one? -9, -5, -1, 1

Which of the following is not a function of the break statement?

Which one? To exit early from a loop To skip the remainder of a switch structure To eliminate the use of certain boolean variables in a loop To ignore certain values for variables and continue with the next iteration of a loop

Which of the following loops is guaranteed to execute at least once?

Which one? counter-controlled while loop for loop This one do...while loop sentinel-controlled while loop

int i; for (i = 0; i <= 10; i++) System.out.println( " * " ); System.out.println( " ! " ); Which of the following is the update expression in the for loop above?

Which one? i = 0; i <= 10; this one? i++; System.out.println("*");

Which one? "First exam is on Monday." This one? "F#rst exam #s on Monday." "F#rst exam is on Monday." "#i### #### i###########."

int x = 27; int y = 10; do x = x / 3; while (x >= y); If y = 0, how many times would the loop above execute?

Which one? 1 2 3 this one? 4

counter controlled loop

a loop whose processing is controlled by a counter; the loop body will be processed a precise number of times

Suppose that alpha and beta are int variables. The statement alpha = --beta; is equivalent ot the statement(s)___.

beta = beta - 1; alpha = beta;

True or false: Because a do...while loop is a post-test loop, the body of the loop may not execute at all.

false

True or false: In Java "| |" has a higher precedence than "&&"

false

True or false: The method printf is used only to format the output of integers and decimal numbers.

false

True or false: When one control statement is located within another, it is said to be a controlled statement.

false

True or false: the calss JOptionPane is part of the package java.swing.

false

boolean found = false; int num; int square; while (!found) { num = console.nextInt(); square = num * num; if (square > 40) found = true; } The above code is an example of a(n) ____ loop.

flag controlled loop

int sum = 0; int limit = console.nextInt(); int counter = 0; while (counter <= limit) { entry = console.nextInt(); sum = sum + entry; counter++; } System.out.println(sum); The above code is an example of a(n) ____ while loop.

flag-controlled This one counter-controlled EOF-controlled sentinel-controlled

What does >= mean?

greater than or equal to

Which of the following will cause a syntax error, if you are trying to compare x to 5?

if (x == 5) This one? if (x = 5) if (x <= 5) if (x >= 5)

Which of the following is a valid statement? (i) int num = new int( 67 ); (ii) String name = new ( " Doe " ); (iii) String name = " Doe " ;

iii

The declaration int a, b, c; is equivalent to which of the following?

int a , b c; this one int a; int b; int c; int abc; int a b c;

Which package is automatically imported by the Java system?

java.io this one java.lang java.util java.swing

In a_____ control structure, the computer executes particular statements depending on some condition(s).

looping, repetition, selection, sequence ???

Suppose str is a String variable. The statement str = new String("Programming"); is simmilar to which of the following?

new String = "Programming"; String new = "Programming"; this one str = "Programming"; str new "Programming";

switch (lastInitial) { case ' A ' : System.out.println( " section 1 " ); break; case ' B ' : System.out.println( " section 2 " ); break; case ' C ' : System.out.println( " section 3 " ); break; case ' D ' : System.out.println( " section 4 " ); break; default: System.out.println( " section 5 " ); } Based on the code above, what is the output if lastInitial = 'c'?

section 3

In a ____ control structure, the computer executes particular statements depending on some condition(s).

selection

static final int EndVal = -1; int double; int num = console.nextInt(); while (num != EndVal) { double = num * 2; System.out.println(double); num = console.nextInt(); } The above code is an example of a(n) ____ while loop.

sentinel-controlled

ch = inFile.next().charAt(); while (inFile.hasNext()) { System.out.println(ch); ch = inFile.next().charAt(); } The above code is an example of a(n) ____ loop.

sentinel-controlled flag-controlled this one? it's a file reader EOF-controlled counter-controlled

Suppose the String variable str points to the String object "Sunny day" at the memory address 3600. Then the value of str is:

the memory address 3600 "Sunny day" 3600 + "Sunny day" None of these

The conditional operator ?: takes _____ arguments.

two three four five

What is the output of the following Java code? int x = 0; if (x > 0) System.out.println("positive "); System.out.println("zero "); System.out.println("negative");

CSI midterm

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