Skip to content

Commit 63e0be6

Browse files
author
Ram swaroop
committed
constructors: added content (60% done)
1 parent 0737af0 commit 63e0be6

1 file changed

Lines changed: 96 additions & 4 deletions

File tree

‎_posts/2015-06-30-constructors.md‎

Lines changed: 96 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -9,10 +9,11 @@ constructor of the object's actual class type, but also the constructor of each
99
Suppose there is a `Horse` class which extends `Animal` (and obviously `Animal` extends `Object`). Now this is how the
1010
constructors are called after `new Horse()` is invoked from `main()`:
1111

12-
1. main() calls new Horse()
13-
2. Horse() calls super()
14-
3. Animal() calls super()
15-
4. Object()
12+
-----------------------------|
13+
1. main() calls new Horse() |
14+
2. Horse() calls super() |
15+
3. Animal() calls super() |
16+
4. Object() |
1617

1718

1819
Constructors __have no return type__ and their __names must exactly match the class name__. Typically, constructors
@@ -30,9 +31,100 @@ class Foo {
3031
}
3132
{% endhighlight %}
3233

34+
So when you invoke __`new Foo("rohit", 12)`__, an object of `Foo` class is created with `name` set as `Rohit` and `size`
35+
as `12`.
3336

37+
### Below are the important rules for Constructors:
3438

39+
__1.__ If you don't type a constructor into your class code, a default constructor will be automatically generated by
40+
the compiler. The default constructor is ALWAYS a no-arg constructor.
3541

42+
<table>
43+
44+
<tr>
45+
<th>
46+
Class Code (WhatYouType)
47+
</th>
48+
<th>
49+
Compiler Generated Constructor Code
50+
</th>
51+
</tr>
52+
53+
54+
55+
<tr>
56+
<td>
57+
{% highlight java %}
58+
class Foo {
59+
60+
}
61+
{% endhighlight %}
62+
</td>
63+
<td>
64+
{% highlight java %}
65+
class Foo {
66+
Foo() {
67+
super();
68+
}
69+
}
70+
{% endhighlight %}
71+
</td>
72+
</tr>
73+
74+
75+
<tr>
76+
<td>
77+
{% highlight java %}
78+
public class Foo {
79+
80+
}
81+
{% endhighlight %}
82+
</td>
83+
<td>
84+
{% highlight java %}
85+
public class Foo {
86+
public Foo() {
87+
super();
88+
}
89+
}
90+
{% endhighlight %}
91+
</td>
92+
</tr>
93+
94+
95+
</table>
96+
97+
__2.__ Every constructor has, as its first statement, either a call to an overloaded constructor (`this()`) or a call to the
98+
superclass constructor (`super()`), and if not it is inserted by the compiler.
99+
100+
101+
<table>
102+
103+
<tr>
104+
<td>
105+
{% highlight java %}
106+
class Foo {
107+
Foo() { }
108+
}
109+
{% endhighlight %}
110+
</td>
111+
<td>
112+
{% highlight java %}
113+
class Foo {
114+
Foo() {
115+
super();
116+
}
117+
}
118+
{% endhighlight %}
119+
</td>
120+
</tr>
121+
122+
</table>
123+
124+
__3.__
125+
126+
127+
{% include responsive_ad.html %}
36128

37129
### Q&A
38130

0 commit comments

Comments
 (0)