java generic type class code example

Example 1: java generic type method

// generic methods

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

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

// bounded generics

public  List fromArrayToList(T[] a) {
	    ...
	}

//multiple bounds



// upper bound wildcards

public static void paintAllBuildings(List buildings) {
	    ...
	}
    
// lower bound wildcard

Example 2: java generics type

Java Generic Type Naming convention helps us understanding code easily and having a naming convention is one of the best practices of Java programming language. So generics also comes with its own naming conventions. Usually, type parameter names are single, uppercase letters to make it easily distinguishable from java variables. The most commonly used type parameter names are:

E – Element (used extensively by the Java Collections Framework, for example ArrayList, Set etc.)
K – Key (Used in Map)
N – Number
T – Type
V – Value (Used in Map)
S,U,V etc. – 2nd, 3rd, 4th types