RuntimeException子类
有时候总是会区分不清哪些异常类是RuntimeException的子类，这里特意去源码里面找来整理一下，方便后续查阅，由于RuntimeException在java.lang包下，所以这里也只介绍java.lang包下的RuntimeException子类，通常java.lang包下的异常子类也是遇到比较多的
下面逐一介绍每个子类发生的场景
ArithmeticException
当出现异常的运算条件时，抛出此异常。例如，一个整数"除以零"时，抛出此类的一个实例。
Thrown when an exceptional arithmetic condition has occurred. For example, an integer "divide by zero" throws an instance of this class.
ArrayIndexOutOfBoundsException
用非法索引访问数组时抛出的异常。如果索引为负或大于等于数组大小，则该索引为非法索引。
Thrown to indicate that an array has been accessed with an illegal index. The index is either negative or greater than or equal to the size of the array.
ArrayStoreException
试图将错误类型的对象存储到一个对象数组时抛出的异常。
Thrown to indicate that an attempt has been made to store the wrong type of object into an array of objects. For example, the following code generates an
ArrayStoreException:
Object x[] = new String[3];
x[0] = new Integer(0);
ClassCastException
当试图将对象强制转换为不是实例的子类时，抛出该异常。
Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance. For example, the following code generates a
ClassCastException:
Object x = new Integer(0);
System.out.println((String)x);
EnumConstantNotPresentException
Thrown when an application tries to access an enum constant by name and the enum type contains no constant with the specified name.
This exception can be thrown by the {@linkplain java.lang.reflect.AnnotatedElement API used to read annotations reflectively}.
IllegalArgumentException
抛出的异常表明向方法传递了一个不合法或不正确的参数。
Thrown to indicate that a method has been passed an illegal or inappropriate argument.
IllegalMonitorStateException
抛出的异常表明某一线程已经试图等待对象的监视器，或者试图通知其他正在等待对象的监视器而本身没有指定监视器的线程。
Thrown to indicate that a thread has attempted to wait on an object's monitor or to notify other threads waiting on an object's monitor without owning the specified monitor.
IllegalStateException
在非法或不适当的时间调用方法时产生的信号。换句话说，即 Java 环境或 Java 应用程序没有处于请求操作所要求的适当状态下。
Signals that a method has been invoked at an illegal or inappropriate time. In other words, the Java environment or Java application is not in an appropriate state for the requested operation.
IllegalThreadStateException
线程没有处于请求操作所要求的适当状态时抛出的异常。
Thrown to indicate that a thread is not in an appropriate state for the requested operation. See, for example, the
suspend and resume methods in class Thread.
IndexOutOfBoundsException
指示某排序索引（例如对数组、字符串或向量的排序）超出范围时抛出。
Thrown to indicate that an index of some sort (such as to an array, to a string, or to a vector) is out of range.
NegativeArraySizeException
如果应用程序试图创建大小为负的数组，则抛出该异常。
Thrown if an application tries to create an array with negative size.
NullPointerException
当应用程序试图在需要对象的地方使用 null 时，抛出该异常
Thrown when an application attempts to use {@code null} in a case where an object is required. These include:
were an array.
value.
Applications should throw instances of this class to indicate other illegal uses of the {@code null} object.
{@code NullPointerException} objects may be constructed by the virtual machine as if {@linkplain Throwable#Throwable(String, Throwable, boolean, boolean) suppression were disabled and/or the stack trace was not writable}.
NumberFormatException
当应用程序试图将字符串转换成一种数值类型，但该字符串不能转换为适当格式时，抛出该异常。
Thrown to indicate that the application has attempted to convert a string to one of the numeric types, but that the string does not have the appropriate format.
SecurityException
由安全管理器抛出的异常，指示存在安全侵犯。
Thrown by the security manager to indicate a security violation.
StringIndexOutOfBoundsException
此异常由 String 方法抛出，指示索引或者为负，或者超出字符串的大小。
Thrown by {@code String} methods to indicate that an index is either negative or greater than the size of the string. For some methods such as the charAt method, this exception also is thrown when the index is equal to the size of the string.
TypeNotPresentException
Thrown when an application tries to access a type using a string representing the type's name, but no definition for the type with the specified name can be found. This exception differs from {@link ClassNotFoundException} in that ClassNotFoundException is a checked exception, whereas this exception is unchecked.
Note that this exception may be used when undefined type variables are accessed as well as when types (e.g., classes, interfaces or annotation types) are loaded.
In particular, this exception can be thrown by the {@linkplain java.lang.reflect.AnnotatedElement API used to read annotations reflectively}.
UnsupportedOperationException
当不支持请求的操作时，抛出该异常。
Thrown to indicate that the requested operation is not supported.
如何通过IDEA查找类及子类源码
我用的是IDEA 2020版本，首先全局搜索你想要查找的父类，比如 RuntimeException
Ctrl+鼠标左键点击1处的RuntimeException，可以直接RuntimeException类
点击红框可以看到所有继承RuntimeException的子类，包括我们想要看的java.lang包下的子类
这个时候点击1处可以看到，
下滑即可找到我们想要看的java.lang下的RuntimeException的子类，同样的方法也可以去查看Exception的子类，如图
通过阅读源码可以让我们更深入的理解父类子类关系，在工作中多看多用，知识自然就记忆不忘了。
