为什么在读取数据时不需要使用try-catch块，但是在将扫描仪附加到文件时却需要使用try-catch呢？

Question

Im reading a programming book on The Scanner, and it's saying that we don't need to use try-catch block when reading data because IOException are captured, but we do need try-catch when attaching a Scanner to a file.

for example, in the following code the try-catch is needed. Can you show me an example where try-catch isn't needed but the error is captured by IOException?

Scanner scnaFile = null;
String fileName = "dataFile.txt";
try{
    scanFile = new Scanner(new File(fileName));
} catch (FileNotFoundException ex){
     System.err.println(filename + " not found");
     System.exit(1);
}

Answer 1

Can you show me an example where try-catch isn't needed but the error is captured by IOException?

Example:

Scanner sc = new Scanner(new File("myNumbers"));  
while (sc.hasNextLong()) {  
   long aLong = sc.nextLong();  
}  

These nextXXX methods will not thrown any exception related to I/O as this is captured in the code.
They will throw an exception though if the input is exausted.
Read the Scanner Javadoc