Introduction
Generic type is a special type in Java that allows specific data type as a parameter. The generic type is useful to specify the data type in a class instead of making separated classes for each type. This is the comparison between class creation without using generic type and class creation with generic type.
// without generic type, the class for each type is created
class IntBox {
private int content;
}
class StringBox {
private String content;
}
// with generic type with <T> syntax
class Box<T> {
private T content;
}
Creating Generic Type
This is the basic syntax of using generic type
class_name<T1,T2,....,n>
The generic type is declared by using <T> syntax (the T character can be changed with other character, usually the T character is used to define generic). In this example, the generic type is implemented in a class called Box.
// create a class called Box with generic type called "T"
public class Box<T> {
// using "T" as generic type
private T content;
// constructor
public Box(T content) {
this.content = content;
}
public T getContent() {
return content;
}
public void setContent(T content) {
this.content = content;
}
}
Main Class
public class MyApp {
public static void main(String[] args) {
// using String as a data type
Box<String> stringBox = new Box<>("Generic is Cool!");
// using Integer as a data type
Box<Integer> intBox = new Box<>(12);
// print out the content
System.out.println(stringBox.getContent());
System.out.println(intBox.getContent());
}
}
Output
Generic is Cool!
12
Based on the code above, the data type is specified inside the angle bracket (<>). The data type that can be used is a reference data type.
In this example, the multiple generic type is used in class called Pair.
public class Pair<K,V> {
private K key;
private V value;
public Pair(K key, V value) {
this.key = key;
this.value = value;
}
public K getKey() {
return key;
}
public void setKey(K key) {
this.key = key;
}
public V getValue() {
return value;
}
public void setValue(V value) {
this.value = value;
}
}
Based on the code above, the multiple generic type (<K,V>) is used.
Main Class
public class MyApp {
public static void main(String[] args) {
Pair<Integer, String> myPair = new Pair<>(1,"Test");
// get the key and value
System.out.println(myPair.getKey());
System.out.println(myPair.getValue());
}
}
Output
1
Test
Based on the code above, the required types is define inside angle bracket separated by comma (,).
Sources
- Learn more about generic type in this link.
I hope this article is helpful for learning the Java programming language. If you have any thoughts or comments you can write in the discussion section below.
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