How to catch exception in java

In Java, any statement that may throw an exception can be caught with try...catch. Put statements that may cause exceptions in try { ... }, and then use catch to capture the corresponding Exception and its subclasses.

Multiple catch statements

You can use multiple catch statements, each catch captures the corresponding Exception and its Subclass. After the JVM catches the exception, it will match the catch statement from top to bottom. After matching a certain catch, it will execute the catch code block and then no longer continue to match.                                                                                                                                                                                                                    (Recommended Learning: java Course)

Simply put: only one of multiple catch statements can be executed. For example:

public static void main(String[] args) {    try {
        process1();
        process2();
        process3();
    } catch (IOException e) {
        System.out.println(e);
    } catch (NumberFormatException e) {
        System.out.println(e);
    }
}

When there are multiple catches, the order of the catches is very important: the subclass must be written first. For example:

public static void main(String[] args) {
    try {
        process1();
        process2();
        process3();
    } catch (IOException e) {
        System.out.println("IO error");
    } catch (UnsupportedEncodingException e) { // 永远捕获不到
        System.out.println("Bad encoding");
    }
}

For the above code, the UnsupportedEncodingException exception can never be caught because it is a subclass of IOException. When an UnsupportedEncodingException exception is thrown, it will be caught and executed by catch (IOException e) { ... }.

Therefore, the correct way to write it is to put the subclass first:

public static void main(String[] args) {    try {
        process1();
        process2();
        process3();
    } catch (UnsupportedEncodingException e) {
        System.out.println("Bad encoding");
    } catch (IOException e) {
        System.out.println("IO error");
    }
}

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