Try/Catch 块中的构造函数

Question

The question is about the result of the below code. The answer is compilation error. However I really do not understand why we can't have constructor in try/catch block. I will put the the code below:

public class Test {
    try {
        public Test() {
            System.out.println("GeeksforGeeks");
            throw new Exception();
        }
    }
    catch(Exception e) {
        System.out.println("GFG");
    }
    
    public static void main(String [] args) {
        Test test= new Test();
    }
}

Answer 1

Because the assignments are statements and statements are allowed only inside blocks of code(methods, constructors, static initializers, etc.) here's the clean code

public class Test {

    public Test()throws Exception {
        System.out.println("GeeksforGeeks");
        throw new Exception();
    }



public static void main(String [] args) {
    try {
        Test test= new Test();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

}

Answer 2

Because a constructor is a declaration, not a statement.

Your constructor can be called by other code, but merely declaring it does not execute it; that's what new Test() does. Nothing is executed merely by declaring the constructor, so there is nothing that can throw an exception. Thus, there is nothing to catch.

In more general syntax terms, statements which don't evaluate to a value can only exist in constructors, methods, and initialization blocks.

You can, however, do this:

public static void main(String[] args) {
    try {
        Test test = new Test();
    } catch (Exception e) {
        System.out.println(e);
    }
}

new Test() actually executes the constructor, which is why it may throw an exception and thus you can legally attempt to catch any exception it may throw. Syntactically, all of the above code is inside a method (the main method), which is allowed.