Java generics

// generic methods

public <T> List<T> fromArrayToList(T[] a) {   
	    return Arrays.stream(a).collect(Collectors.toList());
	}

public static <T, G> List<G> fromArrayToList(T[] a, Function<T, G> mapperFunction) {
	    return Arrays.stream(a)
	      .map(mapperFunction)
	      .collect(Collectors.toList());
	}

// bounded generics

public <T extends Number> List<T> fromArrayToList(T[] a) {
	    ...
	}

//multiple bounds

<T extends Number & Comparable>

// upper bound wildcards

public static void paintAllBuildings(List<? extends Building> buildings) {
	    ...
	}
    
// lower bound wildcard

<? super T>

Source: baeldung.com

Java generics

public class Tuple <T> {
  // the T is a placeholder for any datatype
  public T leftValue;
  public T rightValue;
  
  public Tuple(T leftValue, T rightValue){
    // again, T is being used as a placeholder for any type
    this.leftValue = leftValue;
    this.rightValue = rightValue;
}

public class Program{
  public static void main (String args){
    // And upon using Tuples we can fill in the T from the Tuple class with actual datatypes
    Tuple <int> intTuple = new Tuple <int>(5, 500)
    Tuple <String> stringTuple = new Tuple <String> ("Hello", "World")

    // we can even put Tuples inside of Tuples!
    Tuple<Tuple<int>> metaIntTuple = new Tuple <Tuple <int>> (intTuple, new Tuple <int> (456, 0));
  }
}

Similar codes

0 vote276 views1 answer
Spring boot return 201 created
Java Spring
1 vote197 views1 answer
Logging to a file log4j
Java
0 vote230 views2 answers
Adding new field in existing kibana index using spark java
Java
0 vote221 views1 answer
Hashmap get value by key java
Java
0 vote232 views1 answer
Java console readline null pointer exception
Java
2 votes225 views3 answers
Java string to lower case
Java
0 vote232 views5 answers
ArrayList
Java
1 vote239 views1 answer
Spring xml file configuration
Java Spring
0 vote212 views2 answers
R8: java.lang.OutOfMemoryError: GC overhead limit exceeded react-native
Java
0 vote217 views1 answer
How to assert that an exception is thrown java
Java