Thejava.lang.NullPointerExceptionis a runtime exception in Java that occurs when trying to use a variable that does not point to an object and refers to nothing ornull. To use an analogy, it’s like trying to send a letter without specifying the recipient's address. Without an address, ...
publicclassNullPointerExceptionExample{publicstaticvoidmain(String[]args){Stringmessage=null;// 1. 检查对象是否为空if(message!=null){System.out.println(message.length());}else{System.out.println("消息为空");}// 2. 使用Optional类Optional<String>optionalMessage=Optional.ofNullable(message);optionalMe...
Before you can catch an exception, some code somewhere must throw one. Any code can throw an exception: your code, code from a package written by someone else such as the packages that come with the Java platform, or the Javaruntime environment. Regardless of what throws the exception, it...
Example of throw keyword Lets say we have a requirement where we we need to only register the students when their age is less than 12 and weight is less than 40, if any of the condition is not met then the user should get an ArithmeticException with the warning message “Student is not...
at DummyClass.main(DummyClass.java:9) 4. Tries to operate on the array object which is null However, if we try to perform an operation on a null array, the null pointer exception will be thrown. Consider the following example. publicclassDummyClass { ...
In Java, the java.lang.NullPointerException is a popular exception that is faced by programmers while working on web applications and programs. The error is raised when the code tries to access a reference variable that points to a null value. It can be
Regardless of what throws the exception, it's always thrown with the throw statement. As you have probably noticed, the Java platform provides numerous exception classes. All the classes are descendants of the Throwable class, and all allow programs to differentiate among the various types of ...
How to throw exceptions in Java Throwing an exception is as simple as using the "throw" statement. You then specify theExceptionobject you wish to throw. Every Exception includes a message which is a human-readable error description. It can often be related to problems with user input, server...
If your object’s reference equals to null, a NullPointerException will be thrown. Instead, consider using the static String.valueOf method, which does not throw any exceptions and prints "null", in case the function’s argument equals to null. 4. Use the Ternary Operator The ternary ...
1) To avoid NullPointerException we should remember one thing i.e. we must initialize all object references with specified values before using. publicvoid display(String str){if(str.equals("Java")){System.out.println("Java");}} In the above case,NullPointerExceptioncan occur if the paramete...