publicclassDemo{publicstaticvoidmain(String[]args){String mystr=null;System.out.println(mystr.length());}} Output: Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.length()" because "mystr" is nullat com.example.myJavaProject.Demo.main(Demo.java:18) ...
We will see NullPointerException throw if we perform operations with or without null in Java.In a general way we will discuss a few cases and the cases are given below...Case 1: We know that null is cases sensitiveHere, we will see why null is case sensitive in Java and null is a...
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Is NullPointerException checked or unchecked? NullPointerException is anunchecked exceptionand extends RuntimeException class. Hence there is no compulsion for the programmer to catch it. Is FileNotFoundException checked or unchecked? FileNotFoundException isa checked exception in Java. Anytime, we wa...
That is implementation specific, and you won't be able to see the representation ofnullin a pure Java program. (Butnullis represented as a zero machine address / pointer in most if not all Java implementations.) 意思是这个跟Java语言无关,是由Java实现自己去决定的,但大多数实现都是把它放在了...
These exceptions result from programming errors, such as logical errors or incorrect calculations in the code. Common exceptions include: ArithmeticException: When performing invalid arithmetic operations (like division by zero). NullPointerException: This occurs when trying to attempt to use a null ...
Is Java "pass-by-reference" or "pass-by-value"? How do I read / convert an InputStream into a String in Java? Avoiding NullPointerException in Java What are the differences between a HashMap and a Hashtable in Java? How do I generate random integers within a specific range in ...
Java 8 comes with the Optional class in the java.util package for avoiding null return values (and thus NullPointerException). It is very similar to Google Guava’s Optional, which is similar to Nat Pryce’s Maybe class and Scala’s Option class....
NullPointerException is anunchecked exceptionand extends RuntimeException class. Hence there is no compulsion for the programmer to catch it. What is difference between checked and unchecked exception? Difference between Checked and Unchecked Exception ...
Aggregation_Example agrn; String nameClass; char c; Student(String classWhich,char section,Aggregation_Example address) { this.nameClass=classWhich; this.c=section; this.agrn=address; // you havent used in your example which raised a nullpointer exception...