处理未检查异常的Java程序

异常是在运行时出现的问题，导致程序工作的突然流程。记住异常永远不会在编译时抛出，而总是在运行时抛出，无论是任何类型。编译时不会抛出异常。 Throwable 也是所有异常和错误的超类。现在迫切需要处理它们，在Java语言中定义了一个概念，称为“异常处理技术”

有两种类型的异常定义如下

• 检查异常
• 未经检查的异常

真实世界的插图：例外

Consider an employee leaving home for office. He is being monitored by the parent to take ID card stuff and all things as they can think of. Though the employee knows out everything but still being monitored. Now employee leaves out the home still somehow was delayed as his vehicle tyre gets punctured because of which result is that he arrived late to office. Now these wanted things that disrupt his daily routine is referred as Exceptions in Java. Parent actions that helped him though he checked those stuffs but if someday somehow missed and the employee gets things correctly at home itself is referred as ‘checked exception’ in Java. The actions over which parental access does not have any control is referred as ‘unchecked exceptions.’ Here, parent or monitoring authority is referred as ‘Compilers’ in programming languages. Exceptions that can be detected by compilers are checked exceptions and those who can not be detected are called unchecked exceptions.

方法：现在，为了处理异常，提出的概念是异常处理技术。直接潜入 未检查异常的概念。

未经检查的异常

这些类型的异常发生在程序运行期间。这些是编译器在编译时未检查的异常。在Java中 Error 和 Runtime Exception 类下的异常是未经检查的异常，此异常是由于错误的编程而发生的。

1. Errors 类StackOverflow、OutOfMemoryError 异常等异常难以处理
2. 可以在 try-Catch 块的帮助下处理 IndexoutOfBoundException、Nullpointer Exception 等运行时异常

程序员通常会遇到两种主要的未检查异常，即下面将在示例实现的帮助下讨论它们，并讨论如何处理它们。 两种主要方法都提出如下：

1. 索引出界异常
2. 空指针异常

情况 1： (Array)IndexoutOfBoundException ：由于访问的索引大于等于数组长度的大小而发生此异常。发生此异常后，程序将自动终止。简而言之，就是试图访问当前数据结构本身没有保存的内存。这里这个异常是在数据结构上定义的，即“数组”。

Java

// Importing Classes/Files
import java.io.*;
  
class GFG {
  
    // Main Driver Function
    public static void main(String[] args)
    {
        // Array containing 4 elements
        int a[] = { 1, 2, 3, 4 };
  
        // Try to access elements greater than
        // index size of the array
        System.out.println(a[5]);
    }
}

输出：

处理 ArrayIndexoutOfBoundException : Try-catch Block 我们可以处理这个异常try 语句允许您定义要测试错误的代码块，并且catch 块捕获给定的异常对象并执行所需的操作。程序不会终止。

Java

// Importing Classes/Files
import java.io.*;
  
public class GFG {
  
    // Main Driver Method
    public static void main(String[] args)
    {
        // Inserting elements into Array
        int a[] = { 1, 2, 3, 4, 5 };
  
        // Try block for exceptions
        try {
  
            // Forcefully trying to access and print
            // element/s beyond indexes of the array
  
            System.out.println(a[5]);
        }
  
        // Catch block for catching exceptions
        catch (ArrayIndexOutOfBoundsException e) {
  
            // Printing display message when index not
            // present in a array is accessed
            System.out.println(
                "Out of index  please check your code");
        }
    }
}

输出：

情况 2：空指针异常： 尝试访问具有空值的对象引用时会发生此异常。

Java

// Importing Classes/Files
import java.io.*;
  
public class GFG {
    // Main Driver Method
    public static void main(String[] args)
    {
  
        // Instance of string a has null value
        String a = null;
  
        // Comparing null value with the string value
        // throw exception and Print
        System.out.println(a.equals("GFG"));
    }
}

输出：

NullPointerException的处理技术

Java

// Importing Files/Classes
import java.io.*;
  
public class GFG {
  
    // Driver Main Method
    public static void main(String[] args)
    {
        // Assigning NULL to string
        String m = null;
  
        // Try-Catch Block
        try {
            
            // Checking the null value with GFG string
            // and throw exception
            if (m.equals("GFG")) {
                // Print String
                System.out.println("YES");
            }
        }
  
        // Try-Catch Block
        catch (NullPointerException e) {
  
            // Handles the exception
            System.out.println(
                "Object reference cannot be null");
        }
    }
}

输出：