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接口定义
关于java的接口定义方式，以下三种情况下可以采用接口定义方式：
◆接口中声明的变量全部为fnal
和statc类型的，并且这个接口的作用在于定义一些值不能改变的变量。
举个例子：
publc
nterface
ObjectConstants{
publc
statc
fnal
Strng
SPACE
=
new
Strng("
");
publc
statc
fnal
char
FORMFEED
=
'\f';
}
◆接口中只定义可供实现的抽象方法
EventLstener.java
publc
nterface
EventLstener
{
publc
vod
handleEvent(Event
evt);
}
Runnable.java
package
java.lang;
publc
nterface
Runnable
{
publc
abstract
vod
run();
}
◆还有一种方式是上述两种方式的组合，如非必要一般会将这样一个接口定义拆分成两个接口定义
抽象类的定义
1.如果一个类包含一个接口但是不完全实现接口定义的方法，那么该类必须定义成abstract型
例如nputStream.java类的定义方式：
package
java.o;
publc
abstract
class
nputStream
mplements
Closeable
{
//
SKP_BUFFER_size
s
used
to
determne
the
size
of
skpBuffer
prvate
statc
fnal
nt
SKP_BUFFER_size
=
2048;
//
skpBuffer
s
ntalzed
n
skp(long),
f
needed.
prvate
statc
byte[]
skpBuffer;
publc
abstract
nt
read()
throws
OExcepton;
publc
nt
read(byte
b[])
throws
OExcepton
{
return
read(b,
0,
b.length);
}
publc
nt
read(byte
b[],
nt
off,
nt
len)
throws
OExcepton
{
f
(b
==
null)
{
throw
new
NullPonterExcepton();
}
else
f
((off
<
0)
||
(off
>
b.length)
||
(len
<
0)
||
((off
+
len)
>
b.length)
||
((off
+
len)
<
0))
{
throw
new
indexOutOfBoundsExcepton();
}
else
f
(len
==
0)
{
return
0;
}
nt
c
=
read();
f
(c
==
-1)
{
return
-1;
}
b[off]
=
(byte)c;
nt
=
1;
try
{
for
(;
<
len
;
++)
{
c
=
read();
f
(c
==
-1)
{
break;
}
f
(b
!=
null)
{
b[off
+
]
=
(byte)c;
}
}
}
catch
(OExcepton
ee)
{
}
return
;
}
publc
long
skp(long
n)
throws
OExcepton
{
long
remanng
=
n;
nt
nr;
f
(skpBuffer
==
null)
skpBuffer
=
new
byte[SKP_BUFFER_size];
byte[]
localSkpBuffer
=
skpBuffer;
f
(n
<=
0)
{
return
0;
}
whle
(remanng
>
0)
{
nr
=
read(localSkpBuffer,
0,
(nt)
Math.mn(SKP_BUFFER_size,
remanng));
f
(nr
<
0)
{
break;
}
remanng
-=
nr;
}
return
n
-
remanng;
}
publc
nt
avalable()
throws
OExcepton
{
return
0;
}
publc
vod
close()
throws
OExcepton
{}
publc
synchronzed
vod
mark(nt
readlmt)
{}
publc
synchronzed
vod
reset()
throws
OExcepton
{
throw
new
OExcepton("mark/reset
not
supported");
}
publc
boolean
markSupported()
{
return
false;
}
}
2.抽象类的方法体中只定义抽象的方法，例如AbstractMethodError.java
package
java.lang;
publc
class
AbstractMethodError
extends
ncompatbleClassChangeError
{
publc
AbstractMethodError()
{
super();}
publc
AbstractMethodError(Strng
s)
{
super(s);
}
}
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