2026 02 09 BPJ 15-16

Turn in hand-written solutions.

1. Desk

The Desk class has three fields:

• col, a String representing the color;
• price, a double representing the price in dollars;
• messy, a boolean which is true if the desk is messy.

When the desk is built, it is clean, so the constructor should only take in the color and price.

Methods:

• public boolean cheap(): True if the price is less than 20.00.
• public void cleanup(): Make the messy field be false in that desk.
• public static String[] available_colors(): return an array of String: “tan”, “beige”, “brown”.

2. Visibility

Here is a helper class:

class Helper {
    private String a;
    private int b;
    /* constructor omitted. inputs: (String, int) */
    public int core(String c) {
        /* code: if c is "word" return length of a;
                 if c is "num" return b;
                 else return 0 */
    }
    private int alen() { return a.length(); }
    public String seta(String aa) { a = aa; }
    public static void main(String[] args) { /* omitted */ }
}

1. What variables can you access from the main method of the Explain class (below)?
2. What methods/functions can you call from the main method of the Helper class?
3. Write the constructor that is described in the comment.
4. What methods can you call from within the constructor? Explain.

3. Equals vs ==

public class Explain {
    public static void opo (Helper x, String t) {
        String s = "y" + t;
        x.seta(s)
        s += "l";
    }

    public static void rest (int n) { n += 5; }
    public static void quo (String u) {
        u += "est";
        System.out.println(u);
    }

    public static void one() {
        // (6)
        int n = 15, m = 30;
        rest(m);
        // (7)
        String desc = "smoki";
        quo(desc);
        // (8)
        Helper h = new Helper("hache",5);
        opo(h,"ggdrasi");

    }
}

6. Can a function change an int input? After section (6), what are the values of n and m?
7. Can a function change a String input? After section (7), what is the value of desc?
8. After section (8), what is in Helper? List all fields.