Constructor:
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Method
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1. Constructor
is a special method of a class but can’t be invoked directly by method call.
Java
doc. Says (A class contains constructors that are invoked to create objects
from the class blueprint.)
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Methods are member of a class.
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2.
It is not a member of a class as it can
neither be inherited nor invoked using dot (.) operator.
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Dot (.) operator is used to invoke Non static methods via object and
static methods via class name.
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3.
It has no explicit return type.
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It has explicit return type, if there is nothing to return, the
return type must be void
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4.
It has the same name as its class name.
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Can have same name as its class name, but the existence of return
type makes it a method (unfortunately looks like constructor).
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5.
It is used to initialize the objects, members
of object and then execute statements if any.
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Used to execute statements.
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6.
A no-argument, Default constructor is provided
by compiler when no explicit constructor is there. In such case instance
members are initialized with their default values (numeric data types are set
to 0, char to ‘\0’ and reference variable to null).
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Local variable must be initialized explicitly.
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7.
If there is no this() as the first statement,
super() will be there as first statement in the constructor.
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‘this’ is implicitly invoked on all the member in non-static methods,
but need explicit invocation in case of name confliction.
Syntax: this.x, this.go()
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8.
The default constructor will call the default
constructor of its super class due to presence of super() as its first
statement.
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‘super’ can be used to explicitly invoke member of super class
(specially used either in case of name conflict or to call method of super
class when overridden in sub-class )
syntax:
super.member: when name
conflict
super.method(args if any) : when overriden
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9.
A constructor can never be abstract or static.
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A method is of two types defined (implemented) or undefined (abstract). The method implementation can be further
categorized as static or non-static. An abstract method can’t be
static or final.
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10.
Can be specified as public, none (default),
protected or private.
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Access-specifier public, none (default),
protected or private are applicable.
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11.
Can’t be
final,
native, or synchronized. (Constructor can take only access
specifier) |
Can be final, native, static or synchronized.
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12. Can
be invoked by either
a.
new ClassName()
b.
this(args if any)
c.
super(args if any)
d.
getInstance()
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Can be invoked by Class name in case of static
method or by object/this in case of non-static method.
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