1. java.lang.NullPointerException: null pointer exception
A null pointer exception is a null pointer. You have to operate it. Since it points to a null object, it cannot use the method of this object; For example, if the above s is null, you have to use the method of S.
1 package Null pointer; 2 import java.util.Scanner; 3 public class Lianxi { 4 static Scanner x=new Scanner(System.in); 5 private int a; 6 public void set(int a) { 7 this.a=a; 8 } 9 public static void main(String[] args) { 10 Lianxi[] a=new Lianxi[10]; 11 12 for(int i=0;i<10;i++) { 13 a[i].set(x.nextInt()); 14 } 15 } 16 }
error correction
1 //Initialize it 2 public static void main(String[] args) { 3 Lianxi[] a=new Lianxi[10]; 4 for(int i=0;i<10;i++) { 5 a[i]=new Lianxi(); 6 } 7 for(int i=0;i<10;i++) { 8 a[i].set(x.nextInt()); 9 } 10 }
2. ClassCastException - type cast exception.
Animal a1 = new Dog(); // 1 Animal a2 = new Cat(); // 2 Dog d1 = (Dog)a1; // 3 Dog d2 = (Dog)a2; // 4
1 public class ThreadPriorityDemo { 2 public static void main(String[] args) { 3 4 ThreadPriority tp1 = new ThreadPriority(); 5 ThreadPriority tp2 = new ThreadPriority(); 6 ThreadPriority tp3 = new ThreadPriority(); 7 8 tp1.setName("Olaf"); 9 tp2.setName("excavating machinery"); 10 tp3.setName("Deppon Manager"); 11 12 //Get default priority 13 //System.out.println(tp1.getPriority());//5 14 //System.out.println(tp2.getPriority());//5 15 //System.out.println(tp3.getPriority());//5 16 17 //Set priority value 18 //IllegalArgumentException:Illegal parameter exception 19 tp1.setPriority(1000); 20 21 //By viewing API Set the correct priority 22 // tp1.setPriority(1); 23 // tp3.setPriority(10); 24 25 //Start thread 26 // tp1.start(); 27 // tp2.start(); 28 // tp3.start(); 29 } 30 }
Solution: either replace the jdk or download the spring jar package conforming to the jdk again
4. ArithmeticException - arithmetic operation exception
1 public static void main(String[] args) { 2 // The integer 0 is used as the denominator and an arithmetic operation exception is reported 3 System.out.println(1 / 0); 4 }
Solution: check the code and modify the wrong expression.
5. ArrayStoreException - stores an object exception to the array that is incompatible with the declared type
1 public ArrayList(Collection<? extends E> c) { 2 elementData = c.toArray(); 3 if ((size = elementData.length) != 0) { 4 // c.toArray might (incorrectly) not return Object[] (see 6260652) 5 if (elementData.getClass() != Object[].class) 6 elementData = Arrays.copyOf(elementData, size, Object[].class); 7 } else { 8 // replace with empty array. 9 this.elementData = EMPTY_ELEMENTDATA; 10 } 11 }
Solution: put the String Object into the Object variable.
6. IndexOutOfBoundsException - subscript out of bounds exception
Solution: redefine the loop, modify the code, and add constraints
7. NegativeArraySizeException - create an array error exception with a negative size
java.lang.Object
java.lang.Throwable
java.lang.Exception
java.lang.RuntimeException
java.lang.NegativeArraySizeException
This exception is thrown if the application attempts to create an array with a negative size.
8. NumberFormatException - number format exception
1 public static void main(String[] args) { 2 // String“ it"Convert to Integer Of course, it will report abnormal number format 3 System.out.println(Integer.parseInt("it")); 4 }
Solution: generally, there is no problem in transmitting parameters during output.
9. SecurityException - Security Exception
This is an exception caused by ASP.NET security. The possible cause is deployment The server Configured in machine.config on or web.config security policy Modified
Solution: my general solution is to reconfigure the server
10. Unsupported operationexception - unsupported operation exception
public class ListTest {
public static void main(String[] args) {
String[] array = {"1","2","3","4","5"};
List<String> list = Arrays.asList(array);
list.add("6");
}
}
Exceptions are reported when calling the add and remove methods of the List produced by Arrays.asList(). This is caused by Arrays.asList() The returned internal class ArrayList of the city Arrays is not java.util.ArrayList. Both the internal classes ArrayList and java.util.ArrayList of the Arrays inherit AbstractList. Remove, add and other methods. The default throw UnsupportedOperationException in the AbstractList does not do any operation. java.util.ArrayList reproduces these methods, but the internal class ArrayList of the Arrays does not, so Will throw an exception.
solve:
1 public class ListTest { 2 public static void main(String[] args) { 3 String[] array = {"1","2","3","4","5"}; 4 List<String> list = Arrays.asList(array); 5 List arrList = new ArrayList(list); 6 arrList.add("6"); 7 } 8 }
11,
java.lang.AbstractMethodError
Abstract method error. Thrown when an application attempts to call an abstract method.
12,
ava.lang.AssertionError
Assertion error. Used to indicate the failure of an assertion.
13,
java.lang.ClassCircularityError
Class circular dependency error. When initializing a class, throw this exception if circular dependency between classes is detected.
14,
java.lang.ClassFormatError
Class format error. Thrown when the Java virtual machine attempts to read a Java class from a file and detects that the contents of the file do not conform to the valid format of the class.
15,
java.lang.Error
Error. Is the base class for all errors. It is used to identify serious program running problems. These problems usually describe abnormal conditions that should not be caught by the application.
16,
java.lang.ExceptionInInitializerError
Initializer error. Thrown when an exception occurs during the execution of a class's static initializer. A static initializer is a static statement segment directly contained in a class.
17,
java.lang.IllegalAccessError
Illegal access error. This exception is thrown when an application attempts to access, modify a class's field or call its method, but violates the visibility declaration of the field or method.
18,
java.lang.IncompatibleClassChangeError
Incompatible class change error. This exception is thrown when an incompatible change occurs to the class definition on which the method being executed depends. Generally, this error is easily caused when the declaration definition of some classes in the application is modified without recompiling the whole application.
19,
java.lang.InstantiationError
Instantiation error. This exception is thrown when an application attempts to construct an abstract class or interface through Java's new operator
20,
java.lang.InternalError
Internal error. Used to indicate that an internal error has occurred in the Java virtual machine.
21,
java.lang.LinkageError
Link error. This error and all its subclasses indicate that a class depends on other classes. After the class is compiled, the dependent class changes its class definition without recompiling all classes, resulting in an error.
22,
java.lang.NoClassDefFoundError
Class definition error not found. This error is thrown when the Java virtual machine or class loader attempts to instantiate a class and cannot find the definition of the class.
23,
java.lang.NoSuchFieldError
There is no error in the domain. This error is thrown when the application attempts to access or modify a domain of a class and there is no definition of the domain in the definition of the class.
At present, only these have been found and will be supplemented in the future.