java之继承 封装 多态

java之继承 封装 多态
继承

(1)继承是一种联结类的层次模型,并且允许和鼓励类的重用,它提供了一种明确表述共性的方法。

(2)对象的一个新类可以从现有的类中派生,这个过程称为类继承,新类继承了原始类的特性,新类称为原始类的派生类(子类),而原始类称为新类的基类(父类)。

(3)派生类可以从它的基类那里继承方法和实例变量,并且类可以修改或增加新的方法使之更适合特殊的需要。

封装

(1)封装是把过程和数据包围起来,对数据的访问只能通过已定义的界面。面向对象计算始于这个基本概念,即现实世界可以被描绘成一系列完全自治、封装的对象,这些对象通过一个受保护的接口访问其他对象

多态性

(1)多态性是指允许不同类的对象对同一消息作出响应。

(2)多态性包括参数化多态性和包含多态性。

(3)多态性语言具有灵活、抽象、行为共享、代码共享的优势,很好的解决了应用程序函数同名问题。

U2FsdGVkX1+614lO3LPkxSYjc8SwjkjyAjoIl0AQeGEdebmCmJSeqxONi3jfpdlG
OKRVH8VM64tIwP1ztKhB+56tU5lNdf/tLh8DmCpJr+KV3ENA5p6Dbj3PL75/NO5e
WUwBH3ykAFRdxUeFjYMDYDKcv/VmQ+6zD48jNQcuP5wMMjT2SppJd9KK4jog7GvR
/kWSJ84uaFDQHn/ogbQmvaH9L1qge894mUvIL4k/KZRurR3dEIdQT4n5lOo1KmXi
ZXPp7xMk2uMgkebgfXW4gpdHT/tIrswJG9d84805daR3itVtCnEBUg42HxOUezsV
CoV0MxYLSWxc+MPFKm4WnAEqMHz/xm+MRC3SWzJVonesIt+gjZyXkp/l/7q9bUjk
lbz4mvo25R2nb4wgfh5vNPVLmL8GPJlGu2F3JrV5smGF2FNwZQ0kj7vUjOGEDFxY
yc35ydxr/+gxBYG0LTlgxYYDyiI8AwDDX4343TZde9KzhwehhZgd7DwSwjtzeEI7
F/0f+E050XSdv93f4uiGQ2Ei9EIB42kZFOV5uIC3jf4buL2d9Sbi0bPwW782c55G
AkZ0plY1v60NEvy7R4N8ay1mtuscQXGV67pBi2vwnRm6a/dzXMklwHuZD7J5U9ZJ
IXEip0DnICrLXEm+0TOPnFhirRUW+eFdmt+qOYf5R70Ubt200GXTROsa9Qf1XD6Y
C0NQc7q2Joy+UDVg3dcF/XFLHV5Xz4tXlARtg5WDr3EA6GDRAbzkde9tg8ddTicv
Hprd6xivvPkIvNUVooxBahpG5AFjfOdcFMC4D7pXqvzLoM6zLY4FdikDmI1mz0xt
3LsHjlT9AcT7opt+PNEyej2oRNkn651IPmJfluBSMwa0xWJyoaaxsypZPbnlqhZd
HnARxp+vRsJGvFy/W+PA+HtUYYX55UO7vtXFAGlanp/8ckrKg0zs6/eOlX3OCElN
saSPxXmNWSDCVo2tD9jwLYjQMwHSVPLFoEKxfS6otMDZpK6m+twiAAHvJZ7K3Aei
E4MbSrHE6gSU8Oil0US5icbLPMIqWHyHAp5jd1/vstPsnJmGtfGPVObjdxsQQNmG
Q62SpQnJEAD2Rax5YHUKNZ8xJSXb1jV5uyj5uYZlGuKuwVhvnpAxBiJIMleHtahw
KT95n/X86RMbtWQQmvQ2petjS3obpjRTXncqHw1euhhNaVo/RIoiQjyMFI+O3JO3
MzYADP57k+vWTilwWSKtypb24TS6/7mykMxm8H63M3LBeZUpR/9k2Ba5xSIVWUoJ
lm1nxBN8nqwxsTaYqDrHgL1p/YZbxSSLsJTwjUt9hDvv+8jVYVyEXwP7nmj0CdfJ
KlCpKv2WbvxqQ4BxdDKHojaOxz+qRj63snVuri5ZpSVflYzL8/2LYoJgrrjcikrr
51vLMCEl0EEiElAmwAYWB4WYO7p94K6D6zV17Fx8x6hkOrvkWgthKuwO2yXBgSmM
XO+UR9ynaO0fSQGWP/heHj3A6sSKXEbJHpFumwEHjb/5/T1EaS2PSGBYW8eMHAtT
f5sZD3eFjWEfslxCYyV5hRFb3TBZ67mUF1Mb/Ixa3HIUed7j5jcRZ48kLkUc0fB/
4WnrGkpSW8iEvvRkzmv42T7eUhkzL1wjwWBxXcPmPDE0POhYDEc5jVRyXx4/vRQM
lJStQ941h5B1e/TyQDsldgY4FFRUhlKu40B3vr+qmXddIuX6uLW2v/w/01ByxV4o
+eGWr6aDpR7j+4Od53nFslU97TDXINQf4bAsORs5Npn108vjthHKcUqhsCb0VEEs
PH1jR2FQPDkejfOV72KKn6pkePm3wpT7XGZc6LYWyEykcbmY45akDn1TnVIlHVJO
IcsETylajTZgJyNB0v8jiUWyFLsRm2kXVyMSw4goUSoJHebrmDrndeWKBIuqwz0z
KxUzxiNo0Blgk/yjV30zUwNZmdaq/ayUgaErOarkscV7PkvRQOvj/r6v39QOeH4k
0iMW0xmEG0PHNMkOO5+hyEATFdXMNOzbArllvdGQdLJn2Fcp3fJp3IzpfwKIyozk
YAywIO0kfeSQNm5fssxgtpO4zzudzz+XJ2wbEPHQl7Elph0iy6Oqns7gXCEEl2Ul
LmvqXUL+3B6RFqZkZ1h6cDBEPclpfEdI+nYCIB/qvU/NlnDcciaxzVBEkbnMWj4o
H3+b6nYsZpDR6KOqS19YPZ02AmTIb/lllS7llgE2zSpMBNaHld/vRK1vh6n0cxfV
Wwc7aHNrtLebIgoK3oeGRaMVGXXzB6+5+iOICB4iccThRKQ2pk80WcpD36gYrP32
aHomlZ+y46uHNYvEktd1S1tP4Q1nackwwxVkpQGvcisQVGq6dFfusTxLQ21N1pC9
A1q+dewuiJ2oPuVu1IA3IhTPATvIsqZzExmTr6PN4cDSdw/8hMISULrlWFjW9EJA
skpaJtfg8ld2dzX9yCSQXugCzpQfFF5ixSby3b5TOpZ/qnKD+5ZZaS3bS4P4h9k7
HS50dVMDkCFoWn3FnqrfYH1FW5Z5JSJlHpt3OZKJ2my5pVmN2A6a1EKaDE6+ULu0
ZTe1nlQ+/E0UZK2FXGO6BgF0ZzZgyKPeToHwYGzyFqfHrv3/XIBGLqUadl0oGcXh
s9CzHEcHIygv+roObym8sTIZa+A4ZYodSpj40Yaf/xi0r6TjMrEL7VVIZR+dsbx1
OaiCx/NvE8s8xiL/bnxRf84dhGUf8a8qXZidDbZkLasQgnMjQFevZV1u2FlvDgob
ZA9B22XnUcR9gN/Xspvt4hfKOe9daAlZrrBs1qO9KwaHLvPIcQeFj2mBP61SGLRH
QsyZ45IM6WZMdjZcBND30X1UBnMVWVRuW5wZohsKydAcNQhhD1lZJXPL9161JNX1
nygiScj/97Rvpj3oTAPhdtn+zDuH256FTJwMmM2M8wwxJLv5xV7EyohEZfH3EkBJ
Dz/JYUMQaNvXqHJSxRVDw7jsbDTzgPwa5U9+WS66odZnn/TrmXp8D5b3ahx1XAfL
1NGITuqEjv4Ou5UmcmE/sSCsCN8urtZaUylTKwAh0BZbN5j53pd+MLbmjhsgAwG5
Er9AjMIzQD4KqU3UPxFRWoXhI3i5G0X46aDnTBkSKx1hcLNHUBms1aAwtRIzSkUM
yv4gO2zcp2EW7Yp/7H3Iy64xkluWWjHeMpcJwTL484id5IYooXveQIp4bX9m2Bz/
eDL8bs8yYT5Wr9dwC3XfWcckdoZo5rLoezkNFd6UnDQGS0sn88ahbr2kH9AU6rhv
vgVk8DsM6JPBoTTPnudwdvyUkwMbX0ubB7+iYXWQwLIISeEGHr8v9Bxgt8p84shy
MAKt7nX3pfj0Dv60jAX3VqEFcPV4HW5jc2ypg4EvnemyOcj4f274G6xKFg8zBIKk
1EogN9BHE54HQckiKkr8ikN6EFoYzGds24vBAc6aDgzn0xpD8RJd4TnKVdSxmr/4
SdEtbj7PBGCfGkL4UjX/gcFDTSGwrLtcxl/jslG8DMoUR7PaVDJK8DaEGa+vmk7F
1KNg7XcCq9tyr2FvCNiGgGklUiKh1cACx6dwumHDoMeeTzW8O/kSENsKHsYomtV1