Editing Java syntax (section)

====Constructors and initializers====
A [[Constructor (object-oriented programming)|constructor]] is a special method called when an object is initialized. Its purpose is to initialize the members of the object. The main differences between constructors and ordinary methods are that constructors are called only when an instance of the class is created and never return anything. Constructors are declared as common methods, but they are named after the class and no return type is specified:

<syntaxhighlight lang="java">
class Foo {
    String str;

    Foo() { // Constructor with no arguments

        // Initialization
    }

    Foo(String str) { // Constructor with one argument
        this.str = str;
    }
}
</syntaxhighlight>

Initializers are blocks of code that are executed when a class or an instance of a class is created. There are two kinds of initializers, ''static initializers'' and ''instance initializers''.

Static initializers initialize static fields when the class is created. They are declared using the <code>static</code> keyword:

<syntaxhighlight lang="java">
class Foo {
    static {
        // Initialization
    }
}
</syntaxhighlight>

A class is created only once. Therefore, static initializers are not called more than once. On the contrary, instance initializers are automatically called before the call to a constructor every time an instance of the class is created. Unlike constructors instance initializers cannot take any arguments and generally they cannot throw any [[Exception handling#Checked exceptions|checked exceptions]] (except in several special cases). Instance initializers are declared in a block without any keywords:

<syntaxhighlight lang="java">
class Foo {
    {
        // Initialization
    }
}
</syntaxhighlight>

Since Java has a garbage collection mechanism, there are no [[Destructor (computer science)|destructors]]. However, every object has a <code>finalize()</code> method called prior to garbage collection, which can be [[method overriding|overridden]] to implement finalization.