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  1. import java.util.*;
  2. import java.util.function.Predicate;
  3. import java.util.stream.Stream;
  4. import java.lang.*;
  5.  
  6. class TestingJavaStream {
  7.     public static void main(String[] args) {
  8.     	System.out.println(System.getProperty("java.version"));
  9.  
  10.         Message message = new Message();
  11.         message.setName("Hello World!");
  12.  
  13.         Stream<Message> messageStream = streamNonnulls(Collections.singleton(message))
  14.                 .filter(not(Collection::isEmpty))
  15.                 .findFirst()
  16.                 .map(Collection::stream)
  17.                 .orElseGet(Stream::empty);
  18.  
  19.         System.out.println("Number of messages printed are "
  20.                 + messageStream
  21.                         .map(TestingJavaStream::print)
  22.                         .count());
  23.     }
  24.  
  25.     public static class Message {
  26.         private String name;
  27.  
  28.         public String getName() {
  29.             return this.name;
  30.         }
  31.  
  32.         public void setName(String name) {
  33.             this.name = name;
  34.         }
  35.  
  36.         @Override
  37.         public int hashCode() {
  38.             final int prime = 31;
  39.             int result = 1;
  40.             result = prime * result + ((name == null) ? 0 : name.hashCode());
  41.             return result;
  42.         }
  43.  
  44.         @Override
  45.         public boolean equals(Object obj) {
  46.             if (this == obj)
  47.                 return true;
  48.             if (obj == null)
  49.                 return false;
  50.             if (getClass() != obj.getClass())
  51.                 return false;
  52.             Message other = (Message) obj;
  53.             if (name == null) {
  54.                 if (other.name != null)
  55.                     return false;
  56.             } else if (!name.equals(other.name))
  57.                 return false;
  58.             return true;
  59.         }
  60.  
  61.         @Override
  62.         public String toString() {
  63.             return "Message [name=" + name + "]";
  64.         }
  65.  
  66.     }
  67.  
  68.     @SafeVarargs
  69.     public static <T> Stream<T> streamNonnulls(T... in) {
  70.         return stream(in).filter(Objects::nonNull);
  71.     }
  72.  
  73.     @SafeVarargs
  74.     public static <T> Stream<T> stream(T... in) {
  75.         return Optional.ofNullable(in)
  76.                 .filter(arr -> !(arr.length == 1 && arr[0] == null))
  77.                 .map(Stream::of)
  78.                 .orElseGet(Stream::empty);
  79.     }
  80.  
  81.     public static <T> Predicate<T> not(Predicate<T> p) {
  82.         return (T x) -> !p.test(x);
  83.     }
  84.  
  85.     public static Message print(Message someValue) {
  86.         System.out.println("Message is  :: " + someValue.toString());
  87.         return someValue;
  88.     }
  89. }
Success #stdin #stdout 0.14s 49252KB
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Standard input is empty
stdout
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12.0.1
Number of messages printed are 1
https://ideone.com/9mzrx3
language:
Java (HotSpot 12)
created:
1 year ago
visibility:
public

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