抛出运行时异常之前的控制台输出

Question

We have two similar codes which both results in a RunTimeException. However, one of the codes will print out the results + exception while the other one ONLY throws the exception without the results up until the point the exception is thrown. You can see both blocks of code here, one is commented out:

First case:

public class ExceptionTest {

 public static void main(String[] args) {
    String letters = "abcdef";

    System.out.println(letters.length());
    System.out.println(letters.charAt(3));
    System.out.println(letters.charAt(6));

 }
}

Second case :

public class ExceptionTest {

 public static void main(String[] args) {
    int total = 0;
    StringBuilder letters = new StringBuilder ("abcdefgh");
    total += letters.substring(1, 2).length();
    total += letters.substring(6, 6).length();
    total += letters.substring(6, 5).length();

    System.out.println(total);

 }
}

Can anyone explain why it will print only the RuntimeException and not include the results in the commented code block?

Answer 1

The output comes from System.out.println(). In the commented out version the Exception is caused by substring(6,5) I think and that comes before the println().

Answer 2

    String letters = "abcdef";

    System.out.println(letters.length());
    System.out.println(letters.charAt(3));
    System.out.println(letters.charAt(6)); // <--- fails

This code fails at the commented line, after the execution of System.out.println(letters.length()); and System.out.println(letters.charAt(3)); . So you are able to see the two outputs.

int total = 0;

StringBuilder letters = new StringBuilder ("abcdefgh");

total += letters.substring(1, 2).length();
total += letters.substring(6, 6).length();
total += letters.substring(6, 5).length(); //<-- fails

System.out.println(total);

This code fails before System.out.println(total); , so there is no output