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

Chapter 6 Check Point Questions

Section 6.4

▼6.4.1

What are the benefits of using a method?

▼6.4.2

How do you define a method? How do you invoke a method?

▼6.4.3

How do you simplify the max method in Listing 6.1 using the conditional operator?

▼6.4.4

True or false? A call to a method with a void return type is always a statement itself, but a call to a value-returning method cannot be a statement by itself.

▼6.4.5

What is the return type of a main method?

▼6.4.6

What would be wrong with not writing a return statement in a value-returning method? Can you have a return statement in a void method? Does the return statement in the following method cause syntax errors?

public static void xMethod(double x, double y) {   
  System.out.println(x + y);
  return x + y;
}

▼6.4.7

Define the terms parameter, argument, and method signature.

▼6.4.8

Write method headers (not the bodies) for the following methods:
a. Return a sales commission, given the sales amount and the commission rate.
b. Display the calendar for a month, given the month and year.
c. Return a square root of a number.
d. Test whether a number is even, and returning true if it is.
e. Display a message a specified number of times.
f. Return the monthly payment, given the loan amount, number of years, and annual interest rate.
g. Return the corresponding uppercase letter, given a lowercase letter.

▼6.4.9

Identify and correct the errors in the following program:

 1  public class Test {
 2    public static method1(int n, m) {
 3      n += m;
 4      method2(3.4);
 5    }
 6
 7    public static int method2(int n) {
 8      if (n > 0) return 1;
 9      else if (n == 0) return 0;
10      else if (n < 0) return -1;
11    }
12  }

▼6.4.10

Reformat the following program according to the programming style and documentation guidelines proposed in Section 1.9, Programming Style and Documentation. Use the end-of-line brace style.

public class Test {
  public static double method(double i, double j) 
  {
    while (i < j) {
      j--;
    } 

    return j;
  }
}

Section 6.5

▼6.5.1

How is an argument passed to a method? Can the argument have the same name as its parameter?

▼6.5.2

Identify and correct the errors in the following program:

 1   public class Test {
 2     public static void main(String[] args) {
 3       nPrintln(5, "Welcome to Java!");
 4     }
 5
 6     public static void nPrintln(String message, int n) {
 7       int n = 1;
 8       for (int i = 0; i < n; i++)
 9         System.out.println(message);
10     }
11  }

▼6.5.3

What is pass-by-value? Show the result of the following programs.

(a)
public class Test {
  public static void main(String[] args) {
    int max = 0;
    max(1, 2, max);
    System.out.println(max);
  }

  public static void max(
      int value1, int value2, int max) {
    if (value1 > value2)
      max = value1;
    else
      max = value2;
  }
}

(b)
public class Test {
  public static void main(String[] args) {
    int i = 1;
    while (i <= 6) {
      method1(i, 2);
      i++;
    }
  }

  public static void method1(
      int i, int num) {   
    for (int j = 1; j <= i; j++) {
      System.out.print(num + " ");
      num *= 2;
    }
      
    System.out.println();
  }
}

(c)
public class Test {
  public static void main(String[] args) {
    // Initialize times
    int times = 3;
    System.out.println("Before the call,"
      + " variable times is " + times);
  
    // Invoke nPrintln and display times 
    nPrintln("Welcome to Java!", times);
    System.out.println("After the call," 
      + " variable times is " + times);
  }

  // Print the message n times
  public static void nPrintln(
      String message, int n) {
    while (n > 0) {
      System.out.println("n = " + n);
      System.out.println(message);
      n--;
    }
  }
}

(d)
public class Test {
  public static void main(String[] args) {
    int i = 0;
    while (i <= 4) {
      method1(i);
      i++;
    }

    System.out.println("i is " + i);
  }

  public static void method1(int i) {
    do {
      if (i % 3 != 0)
        System.out.print(i + " ");
      i--;
    }
    while (i >= 1);

    System.out.println();
  }
}

▼6.5.4

For (a) in the preceding question, show the contents of the activation records in the call stack just before the method max is invoked, just as max is entered, just before max is returned, and right after max is returned.

Section 6.6

▼6.6.1

Trace the gcd method to find the return value for gcd(4, 6).

▼6.6.2

Trace the isPrime method to find the return value for isPrime(25).

Section 6.7

▼6.7.1

What is hexCharToDecimal('B')? What is hexCharToDecimal('7')? What is hexToDecimal('A9')?

Section 6.8

▼6.8.1

What is method overloading? Is it permissible to define two methods that have the same name but different parameter types? Is it permissible to define two methods in a class that have identical method names and parameter lists but different return value types or different modifiers?

▼6.8.2

What is wrong in the following program?

public class Test {
  public static void method(int x) {
  }
 
  public static int method(int y) {
    return y;
  }
}

▼6.8.3

Given two method definitions,

public static double m(double x, double y)
public static double m(int x, double y)

tell which of the two methods is invoked for:

a.	double z = m(4, 5);
b.	double z = m(4, 5.4);
c.	double z = m(4.5, 5.4);

Section 6.9

▼6.9.1

What is a local variable?

▼6.9.2

What is the scope of a local variable?