Accessor Methods Practice

Sample questions

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1. Sample 1difficulty 1/5

   public class Student {
       private String name;
       public Student(String n) { name = n; }
       public String getName() { return name; }
   }
   // ...
   Student s = new Student("Ana");
   System.out.println(s.getName());

   What is printed?

   • A

     Compile-time error

   • B

     null

   • C

     name

   • D

     Ana

     check_circle

   Why

   The accessor method getName returns the instance variable name, which was set to "Ana" by the constructor.

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2. Sample 2difficulty 2/5

   public class Temp {
       private double celsius;
       public Temp(double c) { celsius = c; }
       public double toFahrenheit() {
           return celsius * 9.0 / 5.0 + 32;
       }
   }
   // ...
   Temp t = new Temp(100);
   System.out.println(t.toFahrenheit());

   What is printed?

   • A

     212.0

     check_circle
   • B

     100.0

   • C

     180.0

   • D

     32.0

   Why

   100 * 9/5 + 32 = 180 + 32 = 212.0.

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3. Sample 3difficulty 3/5

   public class Wrap {
       private StringBuilder b = new StringBuilder("hi");
       public StringBuilder getB() { return b; }
   }
   // ...
   Wrap w = new Wrap();
   w.getB().append("!");
   System.out.println(w.getB());

   What is printed?

   • A

     hi!

     check_circle
   • B

     !

   • C

     hi

   • D

     Compile-time error

   Why

   The getter returns the same mutable reference; appending modifies the underlying StringBuilder.

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4. Sample 4difficulty 3/5

   A typical "getter" for <code>private int age;</code>

   • A

     public int age() { age++; }

   • B

     public void getAge() { return age; }

   • C

     public static int getAge();

   • D

     public int getAge() { return age; }

     check_circle

   Why

   Returns the field; non-static; no parameters.

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5. Sample 5difficulty 3/5

   public class Group {
       private int[] data;
       public Group(int[] d) {
           data = new int[d.length];
           for (int i = 0; i < d.length; i++) data[i] = d[i];
       }
       public int[] getData() {
           int[] copy = new int[data.length];
           for (int i = 0; i < data.length; i++) copy[i] = data[i];
           return copy;
       }
   }
   // ...
   int[] a = {1, 2, 3};
   Group g = new Group(a);
   int[] view = g.getData();
   view[1] = 100;
   System.out.println(a[1] + "," + g.getData()[1]);

   What is printed?

   • A

     2,100

   • B

     100,100

   • C

     100,2

   • D

     2,2

     check_circle

   Why

   Both the constructor and accessor make defensive copies, so neither g's data nor a are affected by changes to view.

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