I have the following java classes:
public class Outer { ... private class Inner { ... } ... } Assume I am inside a non-static method of Outer. Does it make a difference whether I call this.new Inner() or new Outer.Inner()? Is it, in the second case, guaranteed that no new Outer is created?
I have an annoying error in my program that appears only sometimes and is hard to find or to reproduce. So I am wondering if this line could make any problems.
They are the same, though they are both unnecessarily long-winded.
The following 3 versions results in the exact same bytecode:
class Outer { private class Inner { } void foo() { Inner a = this.new Inner(); Inner b = new Outer.Inner(); Inner c = new Inner(); // Recommended way to write it } } Bytecode
0: new #7 // class Outer$Inner 3: dup 4: aload_0 5: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V 8: astore_1 9: new #7 // class Outer$Inner 12: dup 13: aload_0 14: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V 17: astore_2 18: new #7 // class Outer$Inner 21: dup 22: aload_0 23: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V 26: astore_3 Blank lines added to improve clarity.
new Outer.Inner(); is sometimes usefull when instantiating an inner public static class from somewhere else. I think of it like an additional package / scope qualifier.
this.new Inner(), or rather other.new Inner(), is useful when you want the Inner object to be linked to an Outer object other than this, which is similar to how you can access a field using name or this.name, you can write new Inner() or this.new Inner(), makes no difference.
this.new Inner()ornew Outer.Inner(), you can declare your inner class asstaticclass.private static class Innernew Outer().new Inner(). But wouldn't it be more helpful for your search to post the error you are trying to resolve?Outerinstance? Since you do not specify its constructor parameter it is not possible that a custom constructor will be invoked and therefore not possible anotherOuteris created.