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  1. // java 8 lambdas
  2. class Main{
  3.   // Interfaces that are used for lambdas may only contain a single method.
  4.  
  5.   interface A{
  6.     void a(); // No argument nor return
  7.   }
  8.   static A a = ()->{System.out.println("A A");};
  9.  
  10.   interface B{
  11.     void b(String s); // String argument, no return
  12.   }
  13.   static B b = s->{System.out.println(s);};
  14.  
  15.   interface C{
  16.     String c(); // No argument, String return
  17.   }
  18.   static C c = ()->"C C"; // short for ()->{return "C C";};
  19.  
  20.   interface D{
  21.     String d(String s); // String for both the argument and return
  22.   }
  23.   static D d = s->s+" D"; // short for s->{return s+" D";};
  24.  
  25.   // Runnable takes no argument and has no return
  26.   static java.lang.Runnable e = ()->{System.out.println("E E");};
  27.   // Consumer takes arguments, but has no return
  28.   static java.util.function.Consumer<String> f = s->{System.out.println(s);};
  29.   // Supplier takes no arguments, but has a return
  30.   static java.util.function.Supplier<String> g = ()->"G G"; // short for ()->{return "G G";};
  31.   // Function takes arguments, and has a return
  32.   static java.util.function.Function<String, String> h = s->s+" H"; // short for s->{return s+" H";};
  33.  
  34.   interface X{
  35.     String x(String a, String b); // It is also possible to have multiple arguments
  36.   }
  37.   static X x = (a,b)->a+" "+b; // short for (a,b)->{return a+" "+b;};
  38.  
  39.   // It is also possible to chain lambda's. This is called currying, and is useful for codegolfing,
  40.   // because a->b->{...} is 1 byte shorter than (a,b)->{...}
  41.   static java.util.function.Function<String, java.util.function.Function<String, String>> y = a->b->a+" "+b; // short for a->b->{return a+" "+b;};
  42.   // NOTE:
  43.   //  - With no arguments currying-lambdas and interface-lambdas are of equal length: ()->{...} vs ()->{...}
  44.   //  - With 1 argument currying-lambdas and interface-lambdas are of equal length: a->{...} vs a->{...}
  45.   //  - With 2 arguments currying-lambdas are 1 byte shorter than interface-lambdas: a->b->{...} vs (a,b)->{...}
  46.   //  - With 3 arguments currying-lambdas and interface-lambdas are of equal length: a->b->c->{...} vs (a,b,c)->{...}
  47.   //  - With 4 or more arguments currying-lambdas are longer than interface-lambdas: a->b->c->d->{...} vs (a,b,c,d)->{...}
  48.  
  49.   // Using a Void null argument is also useful for code-golfing, because v->{...} is 1 byte shorter than ()->{...}
  50.   interface Z{
  51.     String z(Void v);
  52.   }
  53.   static Z z = v->"Z Z"; // short for v->{return "Z Z";};
  54.  
  55.   public static void main(String[] args){
  56.     a.a();
  57.     b.b("B B");
  58.     System.out.println(c.c());
  59.     System.out.println(d.d("D"));
  60.     e.run(); // Runnable has the run() method to execute the lambda
  61.     f.accept("F F"); // Consumer has the accept(...) method to execute the lambda
  62.     System.out.println(g.get()); // Supplier has the get() method to execute the lambda
  63.     System.out.println(h.apply("H")); // Function has the apply(...) method to execute the lambda
  64.     System.out.println(x.x("X","X"));
  65.     System.out.println(y.apply("Y").apply("Y"));
  66.     System.out.println(z.z(null));
  67.   }
  68. }
Success #stdin #stdout 0.16s 37116KB
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Standard input is empty
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A A
B B
C C
D D
E E
F F
G G
H H
X X
Y Y
Z Z
https://ideone.com/dAHTKO
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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