NullPointerException is a runtime exception, so we don’t need to catch it in the program. NullPointerException is raised in an application when we are trying to do some operation onnullwhere an object is required. Some of the common reasons for NullPointerException in java programs are: I...
publicclassNullPointerExceptionExample{publicstaticvoidmain(String[]args){Stringstr=null;intlength=str.length();// 这里会抛出空指针异常System.out.println("字符串长度:"+length);}} 1. 2. 3. 4. 5. 6. 7. 在上面的代码中,我们创建了一个字符串变量str,并将其初始化为null。然后,我们尝试通过调用...
如果一个数组为null,试图用属性length获得其长度时。 如果一个数组为null,试图访问或修改其中某个元素时。 在需要抛出一个异常对象,而该对象为 null 时。 首先,我们先找到Java.lang.NullPointerException这个类,内容很简单: package java.lang; /** * Thrown when a program tries to access a field or method...
我们可以通过对文字而不是对象调用 equals 来避免 NullPointerException。 // A Java program to demonstrate that we can avoid// NullPointerExceptionimport java.io.*;classGFG{publicstaticvoidmain(String[] args){// Initializing String variable with null valueString ptr =null;// Checking if ptr is nu...
the call togetUSB()will try to return the USB port of a null reference, which will result in aNullPointerExceptionat runtime and stop your program from running further. Imagine if your program was running on a customer's machine; what would your customer say if the program suddenly failed...
But, once we run this program, it will fail with NullPointerException: NullPointerException Definition NullPointerException is a Runtime exception that is thrown when Java tries to call any method on a real object but in runtime this object references to the Null Reference. More details about...
空指针错误 java.lang.NullPointerException 浅谈 使用基本的JAVA数据类型,变量的值要么已经是默认值,如果没有对其正常赋值,程序便不能通过编译,因此使用基本的JAVA数据类型(double,float,boolean,char,int,long)一般不会引起空指针异常。由此可见,空指针异常主要跟与对象的操作相关。
Exception in thread "main" java.lang.NullPointerException 1. 您收到此错误的原因是因为我们正在尝试对str1执行length()操作,str1是null。 一个简单的解决方法是对str1添加空检查,如下所示: private static void simpleNullCheck(String str1) {
But When I run this programme it shows java.lang.NullPointerException. I don't know why. How can avoid this error? Thanks In Advance.My Code: import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.StringTokenizer; ...
23.“NullPointerException” 当程序尝试使用没有赋值的对象引用时,就会出现“NullPointerException”异常。 // A Java program to demonstrate thatinvoking a method // on null causes NullPointerException import java.io.*; classGFG { publicstaticvoidmain(String[] args) ...