Introduction to Java Programming and Data Structures, 11E, Y. Daniel Liang

Chapter 10 Check Point Questions

Section 10.2

▼10.2.1

If you redefine the Loan class in Listing 10.2 without setter methods, is the class immutable?

Section 10.3

▼10.3.1

Is the BMI class defined in Listing 10.4 immutable?

Section 10.4

▼10.4.1

What are common relationships among classes?

▼10.4.2

What is association? What is aggregation? What is composition?

▼10.4.3

What is UML notation of aggregation and composition?

▼10.4.4

Why both aggregation and composition are together referred to as composition?

Section 10.5

▼10.5.1

Replace the statement in line 17 in Listing 10.5 TestCourse.java so that the loop displays each student name followed by a comma except the last student name.

Section 10.6

▼10.6.1

What happens when invoking the pop() method on a stack while size is 0?

Section 10.7

▼10.7.1

Describe primitive-type wrapper classes.

▼10.7.2

Can each of the following statements be compiled?

a.	Integer i = new Integer("23");
b.	Integer i = new Integer(23);
c.	Integer i = Integer.valueOf("23");
d.	Integer i = Integer.parseInt("23", 8);
e.	Double d = new Double();
f.	Double d = Double.valueOf("23.45");
g.	int i = (Integer.valueOf("23")).intValue();
h.	double d = (Double.valueOf("23.4")).doubleValue();
i.	int i = (Double.valueOf("23.4")).intValue();
j.	String s = (Double.valueOf("23.4")).toString();

▼10.7.3

How do you convert an integer into a string? How do you convert a numeric string into an integer? How do you convert a double number into a string? How do you convert a numeric string into a double value?

▼10.7.4

Show the output of the following code.

public class Test {
  public static void main(String[] args) {
    Integer x = new Integer(3);
    System.out.println(x.intValue());
    System.out.println(x.compareTo(new Integer(4)));
  }
}

▼10.7.5

What is the output of the following code?

public class Test {
  public static void main(String[] args) {
    System.out.println(Integer.parseInt("10"));
    System.out.println(Integer.parseInt("10", 10));
    System.out.println(Integer.parseInt("10", 16));
    System.out.println(Integer.parseInt("11"));
    System.out.println(Integer.parseInt("11", 10));
    System.out.println(Integer.parseInt("11", 16));
  }
}

Section 10.8

▼10.8.1

What are autoboxing and autounboxing? Are the following statements correct?

a.	Integer x = 3 + new Integer(5);
b.	Integer x = 3;
c.	Double x = 3;
d.	Double x = 3.0;  
e.	int x = new Integer(3);
f.	int x = new Integer(3) + new Integer(4);

▼10.8.2

Show the output of the following code?

public class Test {
  public static void main(String[] args) {
    Double x = 3.5;
    System.out.println(x.intValue());
    System.out.println(x.compareTo(4.5));
  }
}

Section 10.9

▼10.9.1

What is the output of the following code?

public class Test {
  public static void main(String[] args) {
    java.math.BigInteger x = new java.math.BigInteger("3");
    java.math.BigInteger y = new java.math.BigInteger("7");
    java.math.BigInteger z = x.add(y);
    System.out.println("x is " + x);
    System.out.println("y is " + y);
    System.out.println("z is " + z);
  }
}

Section 10.10

▼10.10.1

Suppose that s1, s2, s3, and s4 are four strings, given as follows:

String s1 = "Welcome to Java";
String s2 = s1;
String s3 = new String("Welcome to Java"); 
String s4 = "Welcome to Java";

What are the results of the following expressions?

a.	s1 == s2
b.	s1 == s3
c.	s1 == s4
d.	s1.equals(s3) 
e.	s1.equals(s4) 
f.	"Welcome to Java".replace("Java", "HTML") 
g.	s1.replace('o', 'T')
h.	s1.replaceAll("o", "T")
i.	s1.replaceFirst("o", "T")
j.	s1.toCharArray()

▼10.10.2

To create the string Welcome to Java, you may use a statement like this:

String s = "Welcome to Java";

or:

String s = new String("Welcome to Java");

Which one is better? Why?

▼10.10.3

What is the output of the following code?

String s1 = "Welcome to Java";
String s2 = s1.replace("o", "abc");
System.out.println(s1);
System.out.println(s2);

▼10.10.4

Let s1 be " Welcome " and s2 be " welcome ". Write the code for the following statements:
a. Replace all occurrences of the character e with E in s1 and assign the new string to s3.
b. Split Welcome to Java and HTML into an array tokens delimited by a space and assign the first two tokens into s1 and s2.

▼10.10.5

Does any method in the String class change the contents of the string?

▼10.10.6

Suppose string s is created using new String(); what is s.length()?

▼10.10.7

How do you convert a char, an array of characters, or a number to a string?

▼10.10.8

Why does the following code cause a NullPointerException?

 1  public class Test {
 2    private String text;
 3
 4    public Test(String s) {
 5      String text  = s;
 6    }
 7
 8    public static void main(String[] args) {
 9      Test test = new Test("ABC");
10      System.out.println(test.text.toLowerCase());
11    }
12  }

▼10.10.9

What is wrong in the following program?

 1  public class Test {
 2    String text;
 3
 4    public void Test(String s) {
 5      text = s;
 6    }
 7
 8    public static void main(String[] args) {
 9      Test test = new Test("ABC");
10      System.out.println(test);
11    }
12  }

▼10.10.10

Show the output of the following code.

public class Test {
  public static void main(String[] args) {
    System.out.println("Hi, ABC, good".matches("ABC "));
    System.out.println("Hi, ABC, good".matches(".*ABC.*"));
    System.out.println("A,B;C".replaceAll(",;", "#"));
    System.out.println("A,B;C".replaceAll("[,;]", "#"));

    String[] tokens = "A,B;C".split("[,;]");
    for (int i = 0; i < tokens.length; i++)
      System.out.print(tokens[i] +  " ");
  }
}

▼10.10.11

Show the output of the following code.

public class Test {
  public static void main(String[] args) {
    String s = "Hi, Good Morning";
    System.out.println(m(s));
  }

  public static int m(String s) {
    int count = 0; 
    for (int i = 0; i < s.length(); i++)
      if (Character.isUpperCase(s.charAt(i)))
        count++;

    return count;
  }
}

Section 10.11

▼10.11.1

What is the difference between StringBuilder and StringBuffer?

▼10.11.2

How do you create a string builder from a string? How do you return a string from a string builder?

▼10.11.3

Write three statements to reverse a string s using the reverse method in the StringBuilder class.

▼10.11.4

Write three statements to delete a substring from a string s of 20 characters, starting at index 4 and ending with index 10. Use the delete method in the StringBuilder class.

▼10.11.5

What is the internal storage for characters in a string and a string builder?

▼10.11.6

Suppose that s1 and s2 are given as follows:

StringBuilder s1 = new StringBuilder("Java");
StringBuilder s2 = new StringBuilder("HTML");

Show the value of s1 after each of the following statements. Assume that the statements are independent.

a.	s1.append(" is fun");
b.	s1.append(s2);
c.	s1.insert(2, "is fun");
d.	s1.insert(1, s2);
e.	s1.charAt(2);
f.	s1.length();
g.	s1.deleteCharAt(3); 
h.	s1.delete(1, 3);
i.	s1.reverse();
j.	s1.replace(1, 3, "Computer");
k.	s1.substring(1, 3);
l.	s1.substring(2);

▼10.11.7

Show the output of the following program:

public class Test {  
  public static void main(String[] args) {
    String s = "Java";
    StringBuilder builder = new StringBuilder(s);
    change(s, builder);

    System.out.println(s);
    System.out.println(builder);
  }

  private static void change(String s, StringBuilder builder) {
    s = s + " and HTML";
    builder.append(" and HTML");
  }
}