Review Exercises (Set A1)

```
String word = "CS170 abcd"; 
int i = 4; 
int j = 20; 
char c = 'd';
```
Assuming the above declarations and assignments have been made, give a literal of the correct type that is equivalent (in the "==" sense) to each of the following:
1. word.length()
  10
2. word.charAt(6)
  'a'
3. c + 5
  105
4. ++i
  5
5. j++ - i++
  16
6. "abcd" == word.substring(6)
  false


public class MyProgram {
  public static void main(String[] args) {
    System.out.println(1 + args[1]);
  }
}

What will be displayed as a result of typing the following on the command line?

$ java MyProgram 20 3.14 CS true↵

13.14

Name the 6 numerical primitive data types in Java, and identify those whose values are stored only approximately in memory.
the six numerical primitive types: byte, short, int, long, float, double
those stored approximately: float, double
Which of the following are legal names for variables in Java?
1. 1stNum
2. num1
3. myChar_
4. $tempBoolean
5. while
(b), (c), and (d); (the first choice is illegal as you can't start a variable name with a digit, the last is illegal as "while" is a reserved word)
The expression (4.2 % 0.25) + (42 % 5) evaluates to what value?
2.2

What does the following code print?

public class Main {    
    public static void main(String[] args) {
        int x = 5;
        int y = 3;
        System.out.println(x+y+"stuff");
        System.out.println("stuff"+x+y);
    }
}

8stuff
stuff53

(Fill in each blank with the appropriate word.) The following contains an example of a _______________ (widening or narrowing) conversion. The conversion shown is accomplished by ________________ (promotion, assignment, or casting).
```
double d = 1.23;
float f = (float) d;
```
narrowing; casting
Convert $-39$ to 8-bit two's complement form.
11011001
Convert $-0.3$ to 32-bit IEEE-754 form.
1 01111101 00110011001100110011010

What does the following code print?

public class Main {    
    public static void main(String[] args) {
        int x = 3;
        int y = 5;
        int z = x++;
        y += --x;
        System.out.println(z);
        System.out.println(y);
    }
}

3
8

If a character has value 76 when treated as an integer, how should it be referred to when using the \u### form?

\u004C
Convert the binary number 11100101101000010000111101110001 to hexadecimal.
E5A10F71₍₁₆₎

What does the following code print?

public class Main {    
    public static void main(String[] args) {
        char c = 'W';
        c = (char) ((( c - 'A' + 5) % 26) + 'A');
        System.out.println(c);
    }
}

Write a truth table for the following expression: (P ^ Q) && (! (P || R))

P   Q   R   P^Q   P||R   !(P||R)   (P^Q)&&(!(P||R))
T   T   T    F      T      F              F
T   T   F    F      T      F              F
T   F   T    T      T      F              F
T   F   F    T      T      F              F
F   T   T    T      T      F              F
F   T   F    T      F      T              T
F   F   T    F      T      F              F
F   F   F    F      F      T              F

What does the following code print?

public class Main {    
    public static void main(String[] args) {
        int x = 1;
        int y = 2;
        int z = 3;
        z = y += 1;
        System.out.println(z);
        System.out.println( (true || false) ? x : y);
    }
}

3
1

What does the following code print?

public class Main {    
    public static void main(String[] args) {
        int x = 1 + 2 * 3;
        switch (x) {
        case 6: System.out.println("A");
        case 7: System.out.println("B");
        case 8: System.out.println("C");
        case 9: System.out.println("D");
        default: System.out.println("E");
        }
        
        if (1 < 0) 
            if (0 < 1) 
                System.out.println("F");
        else
            System.out.println("G");
        System.out.println("H");
    }
}

B
C
D
E
H

What does the following print?

public class Main {    
    public static void main(String[] args) {
        boolean found = false;
        int i = 65;
        while (! found) {
            found = (i % 31 == 0);
            i++;
        }
        System.out.println(i);
    }
}

What does the following print?

public class Main {    
    public static void main(String[] args) {
        int f = 1;
        double d = 2.345;
        System.out.printf("%.1f + %d \" %.2f",d,f,d);
    }
}

2.3 + 1 " 2.35

What does the following print?

public class Main {    
    public static void main(String[] args) {
        for (int i = 0; i < 6; i++) {
            for (int j = i; j > 0; j--) 
                System.out.print(j);
            System.out.println();
        }
    }
}

What does the following print?

public class Main {    
    public static void main(String[] args) {
        int c = 0;
        for (int i = 0; i < 100; i++) {
            if (i % 5 == 0) 
                c++;
        }
        System.out.println(c);
    }
}

How many times will the following print "buzz lightyear"?

public class Main {    
    public static void main(String[] args) {
        int x = 0;
        do {
            x++;
            System.out.println("buzz lightyear");
        } while (x > 0);
    }
}

While tempting to say "To infinity and beyond!", it actually prints exactly $2147483648$ times

Suppose you generate a random double, x, and display it to the console. You then ask the user to type in the value he thinks will sum with this number to equal 1. Storing his response in a double, y, what is wrong with using the following code snippet as a check to see if he was correct?
```
if (y == 1 - x) {
    System.out.println("You were correct!");
}
else {
    System.out.println("Sorry.  You were incorrect.");
}
```
One has compared two doubles using the equality operator, which is inherently dangerous, as doubles are stored only approximately.
Who designed and attempted to build the "Difference Engine" and the "Analytic Engine" (the latter being the device for which Ada Byron, the first programmer, wrote her first program)?
Charles Babbage