Runtime Type identification inwards Java
Determining Type of object at runtime inwards Java agency finding what form of object it is. For those who are non familiar alongside What is a Type inwards Java, Type is the refer of degree e..g for “abc” which is a String object, Type is String. Finding Type of whatever object at runtime is likewise known equally Runtime Type Identification inwards Java. Determining Type becomes increasingly of import for a method which accepts parameter of type java.lang.An object similar compareTo method of the Comparable class. Since ii objects of dissimilar type tin non survive equal to each other if nosotros know how to decide the type of Object from the object itself together with then nosotros can, non solely avoid ClassCastExcpetion simply likewise optimized the equals method. Java provides iii dissimilar ways to uncovering the type of object at runtime e.g. instanceof keyword, getClass() and isInstance() method of java.lang.Class. Out of all iii solely getClass() is the ane which just uncovering Type of object spell others likewise render truthful if Type of object is the super type.
As nosotros all know that Java throws ClassCastException if yous endeavour to cast object into incorrect type, which makes finding type of Object at runtime fifty-fifty to a greater extent than of import for robust Java programs, Though type casting tin survive minimized past times using Generics inwards Java simply yous all the same direct maintain around places where yous quest to cast object.
In this Java tutorial nosotros volition run into examples iii ways of determining type of Object from Java programme itself. On same banknote Java programming linguistic communication does non back upward RTTI(Runtime type Identification) which was C++ capability to uncovering Object type at runtime simply equally I said Java has its ain way of facilitating this.
Determining Type of object at runtime inwards Java agency finding what form of object it is. For those who are non familiar alongside What is a Type inwards Java, Type is the refer of degree e..g for “abc” which is a String object, Type is String. Finding Type of whatever object at runtime is likewise known equally Runtime Type Identification inwards Java. Determining Type becomes increasingly of import for a method which accepts parameter of type java.lang.An object similar compareTo method of the Comparable class. Since ii objects of dissimilar type tin non survive equal to each other if nosotros know how to decide the type of Object from the object itself together with then nosotros can, non solely avoid ClassCastExcpetion simply likewise optimized the equals method. Java provides iii dissimilar ways to uncovering the type of object at runtime e.g. instanceof keyword, getClass() and isInstance() method of java.lang.Class. Out of all iii solely getClass() is the ane which just uncovering Type of object spell others likewise render truthful if Type of object is the super type.
As nosotros all know that Java throws ClassCastException if yous endeavour to cast object into incorrect type, which makes finding type of Object at runtime fifty-fifty to a greater extent than of import for robust Java programs, Though type casting tin survive minimized past times using Generics inwards Java simply yous all the same direct maintain around places where yous quest to cast object.
In this Java tutorial nosotros volition run into examples iii ways of determining type of Object from Java programme itself. On same banknote Java programming linguistic communication does non back upward RTTI(Runtime type Identification) which was C++ capability to uncovering Object type at runtime simply equally I said Java has its ain way of facilitating this.
Java programme to decide Type of object at runtime
Here is examine Java programme which demonstrates Runtime type identification inwards Java or inwards elementary worlds how to uncovering Type of object. It likewise examples that how instanceof, getClass() and isInstance() method plant together with how tin nosotros role them to decide Java object type at runtime. In this Java programme nosotros direct maintain iii classes; Rule, SystemRule together with BusinessRule. Both SystemRule together with BusinessRule are sub degree of Rule. We volition create illustration of all iii classes together with and then endeavour to uncovering right Type for those instances. Reason nosotros are using both Super class together with Sub degree inwards this examine because both instanceof together with isInstance() method of java.lang.Class returns truthful if object is of sub degree together with nosotros are testing against super class. Let’s run into programme right away :
/*** Java programme to decide type of Object at runtime inwards Java.
* yous tin position type of whatever object past times iii ways i..e past times using instanceof,
* getClass() together with isInstance() method of java.lang.Class.
* Java does direct maintain capability to uncovering out type of object simply its non called
* equally RTTI (Runtime type Identification) inwards C++.
*
* @author
*/
public class RuntimeTypeIdentificationTest {
public static void main(String args[]) {
//creating illustration of sub degree together with storing into type of superclass
Rule simpleRule = new BusinessRule();
//determining type of object inwards Java using instanceof keyword
System.out.println("Checking type of object inwards Java using instanceof ==>");
if(simpleRule instanceof Rule){
System.out.println("System dominion is illustration of Rule");
}
if(simpleRule instanceof SystemRule){
System.out.println("System dominion is illustration of SystemRule");
}
if(simpleRule instanceof BusinessRule){
System.out.println("System dominion is illustration of BusinessRule");
}
//determining type of object inwards Java using getClass() method
System.out.println("Checking type of object inwards Java using getClass() ==>");
if(simpleRule.getClass() == Rule.class){
System.out.println("System dominion is illustration of Rule");
}
if(simpleRule.getClass() == SystemRule.class){
System.out.println("System dominion is illustration of SystemRule");
}
if(simpleRule.getClass() == BusinessRule.class){
System.out.println("System dominion is illustration of BusinessRule");
}
//determining type of object inwards Java using isInstance() method
//isInstance() is similar to instanceof operator together with returns truthful even
//if object belongs to sub class.
System.out.println("Checking type of object inwards Java using isInstance() ==>");
if(Rule.class.isInstance(simpleRule)){
System.out.println("SystemRule is illustration of Rule");
}
if(SystemRule.class.isInstance(simpleRule)){
System.out.println("SystemRule is illustration of SystemRule");
}
if(BusinessRule.class.isInstance(simpleRule)){
System.out.println("SystemRule is illustration of BusinessRule");
}
}
}
class Rule{
public void process(){
System.out.println("process method of Rule");
}
}
class SystemRule extends Rule{
@Override
public void process(){
System.out.println("process method of SystemRule class");
}
}
class BusinessRule extends Rule{
@Override
public void process(){
System.out.println("process method of Business Rule class");
}
}
Output:
Checking type of object inwards Java using instanceof ==>
SystemRule is illustration of Rule
SystemRule is illustration of BusinessRule
Checking type of object inwards Java using getClass() ==>
SystemRule is illustration of BusinessRule
Checking type of object inwards Java using isInstance() ==>
SystemRule is illustration of Rule
SystemRule is illustration of BusinessRule
If yous hold back at the output yous volition uncovering that both instanceof keyword together with isInstance() likewise consider sub type object equally of Super Type. Only getClass() method returns strict type identification number together with does non consider sub degree object equally of Super class. That’s ane of the argue programmer prefer to role getClass() over instanceof spell overriding equals method inwards Java.
Important points to retrieve nigh Runtime Type Identification inwards Java
Few points which is worth remembering spell determining Type or Class of object from Java programme during runtime:
1) Always decide Type spell writing methods which direct maintain Object, that non solely reduces mistake simply likewise number inwards robust program. You tin likewise role Generics characteristic to write parameterized method which is improve than method which accepts raw types.
2) Type identification is likewise useful earlier type casting whatever object into around other Type to avoid ClassCastException.
3) Another role of Runtime Type identification is to implement type specific characteristic on method which direct maintain full general Type e.g. Object or whatever interface.
That's it on Runtime type identification or determining Type of object at runtime inwards Java program. nosotros direct maintain seen duo of ways to do this similar instanceof operator, getClass() and in conclusion isInstance() method of java.lang.Class. If yous hold back at the output closely yous mightiness direct maintain figured out that except getClass() other ii ways of finding Type of object likewise render truthful if object is of Super type together with that's why getClass() is the preferred way together with I ever role it spell overriding equals() together with hashCode() methods. Remember Java does non back upward Runtime Type Identification (RTTI) equally supported inwards C++ simply does render few API method to uncovering object at runtime.
Further Learning
Complete Java Masterclass
What is bounded together with unbounded wildcards inwards Generics