K. Rajkumar: JAVA Programming, 1/e

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• JAVA Programming, 1/e

• By: K. Rajkumar

• Publisher: Pearson India

• Pub. Date: May 1, 2013

• Web ISBN-13: 978-9-3-3251787-5

• Pages in Print Edition: 696

• Subscriber Rating: [0 Ratings]

  
  

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关键词：Programming Program Kumar gram Ming JAVA

Listing 4.5. Nested Function Calls

1. //DupGenerator.java
   
2. public class DupGenerator
   
3. {
   
4.   public static String duplicate(String s)
   
5.   {
   
6.     return s + s;
   
7.   }
   
8. 
   
9.   public static void main(String[] args)
   
10.   {
    
11.     String s = duplicate(“Java”);
    
12.     System.out.println(s); // prints Java two times
    
13. 
    
14.     s = duplicate(duplicate(duplicate(“Hello”)));
    
15.     System.out.println(s); // 8 times
    
16.   }
    
17. }

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Listing 4.6. Calculating the Area of Geometric Objects

1. // AreaFunction.java
   
2. 
   
3. import java.io.*;
   
4. 
   
5. public class AreaFunction
   
6. {
   
7.   // receives side and returns area public static int areaSquare(int a)
   
8.   {
   
9.     return a * a;
   
10.   }
    
11. 
    
12.   // receives sides a and b, returns area
    
13.   public static int areaRectangle(int a, int b)
    
14.   {
    
15.     return a * b;
    
16.   }
    
17. 
    
18.   // receives sides a and b, returns area
    
19.   public static double areaTriangle(int a, int b)
    
20.   {
    
21.     return 0.5 * a * b;
    
22.   }
    
23. 
    
24.   // receives radius and returns area
    
25.   public static double areaCircle(int r)
    
26.   {
    
27.     return 2 * 3.1415 * r;
    
28.   }
    
29. 
    
30.   // receives radius and height, returns area
    
31.   public static double areaCylinder(int r, int h)
    
32.   {
    
33.     return 2 * 3.1415 * r * r + 2 * 3.1415 * r * h;
    
34.   }
    
35. 
    
36.   public static void main(String[] args)
    
37.   {
    
38.     int area = areaSquare(5);
    
39.     System.out.println(area);
    
40. 
    
41.     // alternatively println() method can also call a method directly
    
42.     System.out.println(areaSquare(5));
    
43.     System.out.println(areaRectangle(5,3));
    
44.     System.out.println(areaTriangle(5,3));
    
45.     System.out.println(areaCircle(3));
    
46.     System.out.println(areaCylinder(3,4));
    
47.   }
    
48. }

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Listing 4.7. Generate all Prime Numbers from 2 to 500

1. // PrimeNumber.java
   
2. 
   
3. public class PrimeNumber
   
4. {
   
5.   public static boolean isPrime(int n)
   
6.   {
   
7.     boolean prime = true;
   
8.     int max = (int)Math.sqrt(n);
   
9. 
   
10.     for (int i = 2; i <= max; i++)
    
11.     {
    
12.       if (n % i == 0)
    
13.       {
    
14.         prime = false;
    
15.         break;
    
16.       }
    
17.     }
    
18. 
    
19.     return prime;
    
20.   }
    
21. 
    
22.   public static void main(String[] args)
    
23.   {
    
24.     for(int i = 2; i <= 500; i++)
    
25.     {
    
26.       if(isPrime(i))
    
27.         System.out.print(i + “ ”);
    
28.     }
    
29.   }
    
30. }

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Listing 4.8. Factorial Using Loops

1. // Factorial.java
   
2. import java.util.*;
   
3. 
   
4. public class Factorial
   
5. {
   
6.   public static int fact(int n)
   
7.   {
   
8.     int f = 1;
   
9. 
   
10.     if( n == 1)
    
11.       return f;
    
12.     for(int i = 2; i <= n; i++)
    
13.       f = f * i;
    
14. 
    
15.     return f;
    
16.   }
    
17.   public static void main(String[] args)
    
18.   {
    
19.     Scanner sc = new Scanner(System.in);
    
20.     System.out.print(“Enter a number: ”);
    
21.     int n = sc.nextInt();
    
22. 
    
23.     if (n >= 0)
    
24.       System.out.println(“Factorial of ”+ n + “: ” + fact(n));
    
25.   }
    
26. }

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Listing 4.12. Addition Calculator Using Overloading

1. // AdditionCalculator.java
   
2. 
   
3. public class AdditionCalculator
   
4. {
   
5.   public static int add(int i, int j)
   
6.   {
   
7.     return i + j;
   
8.   }
   
9. 
   
10.   public static double add(double i, double j)
    
11.   {
    
12.     return i + j;
    
13.   }
    
14. 
    
15.   public static float add(float i, float j)
    
16.   {
    
17.     return i + j;
    
18.   }
    
19. 
    
20.   public static double add(int i, double j)
    
21.   {
    
22.     return i + j;
    
23.   }
    
24. 
    
25.   public static double add(double i, int j)
    
26.   {
    
27.     return i + j;
    
28.   }
    
29. 
    
30.   public static void main(String[] args)
    
31.   {
    
32.     System.out.println(add(10,20));
    
33.     System.out.println(add(10.0,20.0));
    
34.     System.out.println(add(100.0f,200.0f));
    
35.     System.out.println(add(30,20.0));
    
36.     System.out.println(add(50.0,20));
    
37.   }
    
38. }

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Listing 4.13. Sorting Numbers Application

1. // SortNumbers.java
   
2. 
   
3. import java.io.*;
   
4. 
   
5. public class SortNumbers
   
6. {
   
7.   public static void sort(int[] numbers) // reference numbers will directly modify original array a in main()
   
8.   {
   
9.     // take ith number
   
10.     for (int i = 0; i < numbers.length-1; i++)
    
11.     {
    
12.       // compare ith number with all other jth numbers
    
13.       for (int j = j < numbers.length;
    
14.       {
    
15.         // if second number < first
    
16.         if(numbers[j] < numbers[i])
    
17.         {
    
18.           // interchange
    
19.           int temp;
    
20.           temp = numbers[i];
    
21.           numbers[i] = numbers[j];
    
22.           numbers[j] = temp;
    
23.         }
    
24.       }
    
25.     }
    
26.     // since numbers is a reference to original array, through numbers original array gets sorted, so nothing has to be returned
    
27.   }
    
28. 
    
29.   public static void main(String[ ] args) throws IOException
    
30.   {
    
31.     BufferedReader in = new BufferedReade (new InputStreamReader(System.in));
    
32. 
    
33.     // read n
    
34.     System.out.print(“Enter total no. to be processed: ”);
    
35.     int n = Integer.parseInt(in.readLine());
    
36. 
    
37.     // create array a of n size
    
38.     int[ ] a = new int[n]; // to keep actual numbers
    
39. 
    
40.     // read actual numbers
    
41.     System.out.println(“Enter actual numbers: ”);
    
42.     for (int i = 0; i < n; i++)
    
43.       a[i] = Integer.parseInt(in.readLine());
    
44. 
    
45.     // show
    
46.     System.out.println(“Original numbers before sorting ”);
    
47.     for (int i = 0; i < n; i++)
    
48.       System.out.print( a[i] + “ ”);
    
49. 
    
50.     // call sort() method with array a
    
51.     sort(a);
    
52. 
    
53.     // show sorted sequence
    
54.     System.out.println(“\nSorted sequence of numbers ”);
    
55.     for (int i = 0; i < n; i++)
    
56.       System.out.print( a[i] + “ ”);
    
57.   }
    
58. }

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Listing 4.14. Sort() to Sort Strings

1. Listing 4.14. Sort() to Sort Strings
   
2. 
   
3. public static void sort(String[ ] names)
   
4. {
   
5.   // take ith name
   
6.   for (int i = 0; i < names.length-1; i++)
   
7.   {
   
8.     // compare ith name with all other jth names
   
9.     for (int j = j < names.length; j++)
   
10.     {
    
11.       // if second number < first
    
12.       if(names[j].compareTo(names[i]) < 0)
    
13.       {
    
14.         // interchange values
    
15.         String temp;
    
16.         temp = names[i];
    
17.         names[i] = names[j];
    
18.         names[j] = temp;
    
19.       }
    
20.     }
    
21.   }
    
22. }

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Listing 4.15. Sorting Names

1. Listing 4.15. Sorting Names
   
2. 
   
3. // SortNames.java
   
4. import java.io.*;
   
5. 
   
6. public class SortNames
   
7. {
   
8.   public static void sort(String[] names)
   
9.   {
   
10.     // take ith name
    
11.     for (int i = 0; i < names.length-1; i++)
    
12.     {
    
13.       // compare ith name with all other jth names
    
14.       for (int j = i+1; j < names.length; j++)
    
15.       {
    
16.         // if second number < first
    
17.         if(names[j].compareTo(names[i]) < 0)
    
18.         {
    
19.           // interchange values
    
20.           String temp;
    
21.           temp = names[i];
    
22.           names[i] = names[j];
    
23.           names[j] = temp;
    
24.         }
    
25.       }
    
26.     }
    
27.   }
    
28. 
    
29.   public static void main(String[] args) throws IOException
    
30.   {
    
31.     BufferedReader in = new BufferedReader (new InputStreamReader(System.in));
    
32. 
    
33.     // read numbers
    
34.     System.out.print(“Enter total no. of names to be processed: ”);
    
35.     int n = Integer.parseInt(in.readLine());
    
36.     String a[] = new String[n]; // to keep actual names
    
37. 
    
38.     System.out.println(“Enter actual names: ”);
    
39.     for (int i = 0; i < n; i++)
    
40.       [i] = in.readLine();
    
41. 
    
42.     // sort names
    
43.     sort(a);
    
44. 
    
45.     // show
    
46.     System.out.print(“Sorted names: ”);
    
47.     for (int i = 0; i < n; i++)
    
48.       System.out.print( a[i] + “ ”);
    
49.   }
    
50. }

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Listing 4.16. Recipes Application

1. Listing 4.16. Recipes Application
   
2. 
   
3. // Recipes.java
   
4. 
   
5. public class Recipes
   
6. {
   
7.   public static int calcIngredient( int[] serv, int[][] flour, int column )
   
8.   {
   
9.     int total = 0, i, j;
   
10. 
    
11.     for( i = 0, j = 0; i < serv.length; i++, j++)
    
12.       total = total + serv[i] * flour[j][column]; // only one column in flour required
    
13. 
    
14.     return total;
    
15.   }
    
16. 
    
17.   public static void main(String[] args)
    
18.   {
    
19.     int[ ][ ] recipe = { {2,2,1,0}, {3,0,1,0}, {2,1,2,1}};
    
20.     int[ ] serving = {1, 4, 3};
    
21. 
    
22.     // call to calculate flour
    
23.     int cups = calcIngredient(serving, recipe, 0); // only oth column required
    
24.     System.out.println(“No. of cups of flour required: ” + cups);
    
25. 
    
26.     // call to calculate eggs
    
27.     int eggs = calcIngredient(serving, recipe, 1); // only 1st column required
    
28.     System.out.println(“No. of eggs required: ” + eggs);
    
29. 
    
30.     // call to calculate milk
    
31.     int milk = calcIngredient(serving, recipe, 2); // only 2nd column required
    
32.     System.out.println(“No. of cups of milk required: ” + milk);
    
33. 
    
34.     // call to calculate oil
    
35.     int oil = calcIngredient(serving, recipe, 3); // only 3rd column required
    
36.     System.out.println(“No. of tablespoons of oil required: ” + oil);
    
37.   }
    
38. }

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