fork(1) download
copy 
  1. /* package whatever; // don't place package name! */
  2.  
  3. // Use an instance method reference with different objects. 
  4.  
  5. // A functional interface that takes two reference arguments 
  6. // and returns a boolean result. 
  7. interface MyFunc<T> { 
  8.   boolean func(T v1, T v2); 
  9. } 
  10.  
  11. // A class that stores the temperature high for a day. 
  12. class HighTemp { 
  13.   private int hTemp; 
  14.  
  15.   HighTemp(int ht) { hTemp = ht; } 
  16.  
  17.   // Return true if the invoking HighTemp object has the same 
  18.   // temperature as ht2. 
  19.   boolean sameTemp(HighTemp ht2) { 
  20.     return hTemp == ht2.hTemp; 
  21.   } 
  22.  
  23.   // Return true if the invoking HighTemp object has a temperature 
  24.   // that is less than ht2. 
  25.   boolean lessThanTemp(HighTemp ht2) { 
  26.     return hTemp < ht2.hTemp; 
  27.   } 
  28. } 
  29.  
  30.  
  31. /* Name of the class has to be "Main" only if the class is public. */
  32. class Ideone
  33. {
  34. 	 // A method that returns the number of occurences 
  35.   // of an object for which some criteria, as specified by 
  36.   // the MyFunc parameter, is true. 
  37.   static <T> int counter(T[] vals, MyFunc<T> f, T v) { 
  38.     int count = 0; 
  39.  
  40.     for(int i=0; i < vals.length; i++) 
  41.       if(f.func(vals[i], v)) count++; 
  42.  
  43.     return count;   
  44.   } 
  45.  
  46.  
  47.  
  48. 	public static void main (String[] args) throws java.lang.Exception
  49. 	  { 
  50.     int count; 
  51.  
  52.     // Create an array of HighTemp objects. 
  53.     HighTemp[] weekDayHighs = { new HighTemp(89), new HighTemp(82), 
  54.                                 new HighTemp(90), new HighTemp(89), 
  55.                                 new HighTemp(89), new HighTemp(91), 
  56.                                 new HighTemp(84), new HighTemp(83) }; 
  57.  
  58.     // Use counter() with arrays of the class HighTemp. 
  59.     // Notice that a reference to the instance method 
  60.     // sameTemp() is passed as the second argument. 
  61.     count = counter(weekDayHighs, HighTemp::sameTemp, 
  62.                   new HighTemp(89)); 
  63.     System.out.println(count + " days had a high of 89"); 
  64.  
  65.     // Now, create and use another array of HighTemp objects. 
  66.     HighTemp[] weekDayHighs2 = { new HighTemp(32), new HighTemp(12), 
  67.                                 new HighTemp(24), new HighTemp(19), 
  68.                                 new HighTemp(18), new HighTemp(12), 
  69.                                 new HighTemp(-1), new HighTemp(13) }; 
  70.  
  71.     count = counter(weekDayHighs2, HighTemp::sameTemp, 
  72.                     new HighTemp(12)); 
  73.     System.out.println(count + " days had a high of 12"); 
  74.  
  75.  
  76.     // Now, use lessThanTemp() to find days when temperature was less 
  77.     // that a specified value. 
  78.     count = counter(weekDayHighs, HighTemp::lessThanTemp, 
  79.                     new HighTemp(89)); 
  80.     System.out.println(count + " days had a high less than 89"); 
  81.  
  82.     count = counter(weekDayHighs2, HighTemp::lessThanTemp, 
  83.                     new HighTemp(19)); 
  84.     System.out.println(count + " days had a high of less than 19"); 
  85.   } 
  86. }
Success #stdin #stdout 0.16s 2184192KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
3 days had a high of 89
2 days had a high of 12
3 days had a high less than 89
5 days had a high of less than 19
https://ideone.com/f9CBUb
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!