Question

I have this JUnit test that I need help developing a Interface and Class for, here is the test:

Box b1 = new DefaultBox( "abc" ); Box b2 = new DefaultBox( "def" ); 
Box b3 = new DefaultBox( "" ); 

assertEquals("abc", b1.contents()); 
assertEquals("[abc]", b1.toString()); 
assertTrue(b1.equals(b1)); assertFalse(b1.equals(b2)); 
assertFalse(b1.equals(null)); 
assertEquals("cba", b1.flip().contents()); 
assertEquals("", b3.flip().contents()); 

can anyone help me in developing a Default box class and a box interface to make these test pass? Any help would be most appreciated.

Updates

Ok I am trying to start a constuctor but i keep getting a run time error saying “Implicit super constructor Box() is undefined. Must explicitly invoke another constructor” Here is my class:

import javax.swing.Box;
public class DefaultBox extends Box{
       public DefaultBox(String string) {

    }
}

my Junit test is:

import static org.junit.Assert.*;
import javax.swing.Box;



public class question3_test {

    Box b1 = new DefaultBox( "abc" );
    Box b2 = new DefaultBox( "def" ); 
    Box b3 = new DefaultBox( "" );

    public void testquestion3(){
    assertEquals("abc", b1.contents()); 
    assertEquals("[abc]", b1.toString()); 
    assertTrue(b1.equals(b1)); assertFalse(b1.equals(b2)); 
    assertFalse(b1.equals(null)); 
    assertEquals("cba", b1.flip().contents()); 
    assertEquals("", b3.flip().contents()); 
    }

}

I have tried to remove the “extends Box” but then that gives me a run time error on the Junit test. Can anyone guide me on how to remove this implicit super constructor error?

Answer 1

What kind of help you need? Your question doesn’t seem so complex.

• contents should return the string contained
• toString should put it in brackets
• equals should check if contents are equal
• flip should return a new DefaultBox with reversed content

I suppose this is homework, but the class that you have to implement it’s quite trivial..