[Solved] java.lang.ClassCastException using Generics in Java
Generally when ever we write the Java Logic its better to know the issues during the compile time rather than at run time. If we do not use Generics we might face java.lang.ClassCastException when trying to add an Integer Object instead of String Object and try to retrieve the value and perform an operation on it will cause this exception. How do we overcome this using Generics we will learn from this tutorial.
Lets implement the Logic without using the Generics:
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import java.util.ArrayList; import java.util.List; public class ClassCastExceptionExample { public static void main(String[] args) { String str1 = new String("RC"); String str2 = new String("Selenium"); List strList = new ArrayList();//Without using Generics strList.add(str1); strList.add(str2); strList.add(2);//Adding an integer instead of String String str = (String) strList.get(2); str.substring(0, 2);//Throws ClassCastException of performing an operation on Integer } } |
Executing this Program returns following output in the Console:
Exception in thread “main” java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
at org.h2k.javaprograms.ClassCastExceptionExample.main(ClassCastExceptionExample.java:15)
Lets implement the Logic using the Generics:
In the above program change the Line No:8 as follows:
List<String> strList = new ArrayList<String>();
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import java.util.ArrayList; import java.util.List; public class ClassCastExceptionExample { public static void main(String[] args) { String str1 = new String("RC"); String str2 = new String("Selenium"); List<String> strList = new ArrayList<String>(); strList.add(str1); strList.add(str2); strList.add(2);//Compile Time Error at Line number 13 String str = (String) strList.get(2); str.substring(0, 2);//Throws ClassCastException of performing an operation on Integer } } |
Conclusion:
Therefore implementing Generics avoids ClassCastException During run time. Any issues we can caught during Compile Time.