Java核心 -- Exception + Error

Thrown when an application tries to load in a class through its string name using:
The forName method in class Class.
The findSystemClass method in class ClassLoader.
The loadClass method in class ClassLoader.
but no definition for the class with the specified name could be found.

Thrown if the Java Virtual Machine or a ClassLoader instance tries to load in the definition of a class
(as part of a normal method call or as part of creating a new instance using the new expression) and no definition of the class could be found.
The searched-for class definition existed when the currently executing class was compiled, but the definition can no longer be found.

try {
// 業務程式碼
Thread.sleep(1000L);
} catch (Exception e) {
// 忽略
}

try {
// 業務程式碼
} catch (IOException e) {
// Prints this throwable and its backtrace to the standard error stream.
e.printStackTrace();
}

public static void main(String[] args) throws FileNotFoundException {
readFile(null);
}

private static void readFile(String fileName) throws FileNotFoundException {
InputStream in = new FileInputStream(fileName);
}

// 異常資訊不直觀
Exception in thread "main" java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.java:130)
at java.io.FileInputStream.<init>(FileInputStream.java:93)
at me.zhongmingmao.Main.readFile(Main.java:14)
at me.zhongmingmao.Main.main(Main.java:9)

public static void main(String[] args) throws FileNotFoundException {
readFile(null);
}

private static void readFile(String fileName) throws FileNotFoundException {
Objects.requireNonNull(fileName);
InputStream in = new FileInputStream(fileName);
}

// 使用Throw early，異常資訊比較直觀
Exception in thread "main" java.lang.NullPointerException
at java.util.Objects.requireNonNull(Objects.java:203)
at me.zhongmingmao.Main.readFile(Main.java:14)
at me.zhongmingmao.Main.main(Main.java:10)