Can C# style object initialization be used in Java?

Question

In C# it's possible to write:

MyClass obj = new MyClass() {     field1 = "hello",     field2 = "world",     field3 = new MyOtherClass()     {         etc....     } } 

I can see that array initialization can be done in a similar way but can something similar to the above be done in Java too, and if so, what's the syntax?

Answer 1

That initialization syntax is not present in Java.

A similar approach is to use double brace initialization, where you create an anonymous inner sub class with an initializer block:

MyClass obj = new MyClass() {{   // in Java these would be more like this: setFieldX(value);   field1 = "hello";   field2 = "world";   field3 = new MyOtherClass() ... }}; 

Be aware though, that you're actually creating a subclass.

Another approach is to create a builder for MyClass, and have code like this:

MyClass obj = new MyClassBuilder().   withField1("hello").   withField2("world").   withField3(new MyOtherClass()).   build(); 

Answer 2

Java does not have the capability built in to instantiate an object using the shorter syntax. The C# compiler handles this and separates out the property setters in the IL. Until the Java langauge devs decide this is important, you will not be able to take this shortcut.