[英]how to extend a abstract class in java
I have a made an engine class that is as follows. 我有一个引擎类,如下所示。 based on
基于
Engine: Interface that extends Java's Comparable (to compare among engines) and declares an integer getter method “getForce”, which indicatesthat engine subclasses will have a force they are capable of 引擎:扩展Java的Comparable(在引擎之间进行比较)并声明整数getter方法“ getForce”的接口,该方法指示引擎子类将具有它们能够执行的作用力
producing. 生产。
public interface Engine extends Comparable<Engine>{
public int getForce();
}
I am trying to make an AbstractEngine
class based on the following description. 我正在尝试根据以下描述创建一个
AbstractEngine
类。
AbstractEngine
: Abstract class implemented by most engines. AbstractEngine
:大多数引擎实现的抽象类。 It subclasses from Engine and has an integer field indicating its force. 它是Engine的子类,并具有指示其作用力的整数字段。 This field is initialized through a constructor.
该字段通过构造函数初始化。 The class overrides
getForce
from Engine
and compareTo
from Comparable
. 类覆盖
getForce
从Engine
和compareTo
从Comparable
。 The comparison of two engines is done by finding the difference between their forces (in such a way that sorting a collection of engines arranges. I am confused on overriding the methods from Engine
and making sure AbstractEngine
has the compare to the Engine
has. 比较两个引擎是通过找到它们之间的力差来进行的(以排序引擎集合的方式进行排列。我对重写
Engine
的方法感到困惑,并确保AbstractEngine
具有与Engine
比较的能力。
This is what I have at the moment, but it's failing a JUnit test checking if AbstractEngine
has the getForce
, equals
, and CompareTo
. 这是我目前所拥有的,但是它无法通过JUnit测试来检查
AbstractEngine
是否具有getForce
, equals
和CompareTo
。 Is there a specific way I have to extend the methods? 我有扩展方法的特定方法吗?
abstract class AbstractEngine implements Engine {
public AbstractEngine(int force){
}
public int compareTo(Engine o) {
// TODO Auto-generated method stub
return 0;
}
}
here is the junit test 这是junit测试
import static org.junit.Assert.*;
import org.junit.Test;
public class EngineTest {
@Test
public void test0_EngineImplementsComparableAndDefinesGetForce() {
Engine engine = new Engine() {
@Override
public int compareTo(Engine o) {
return 0;
}
@Override
public int getForce() {
return 0;
}
};
assertTrue( "Incorrect result", engine instanceof Comparable );
}
@Test
public void test1_AbstractEngineIsAnEngine() {
Engine engine = new AbstractEngine( 2 ) { };
assertTrue( "Incorrect result", engine instanceof Engine );
}
@Test
public void test2_AbstractEngineHasGetForce() {
Engine engine = new AbstractEngine( 24 ) { };
int actual = engine.getForce();
int expected = 24;
assertEquals( "Incorrect result", expected, actual );
}
@Test
public void test3_AbstractEngineHasEquals() {
Engine a, b;
boolean actual;
// equal to itself
a = new AbstractEngine( 42 ) { };
actual = a.equals( a );
assertTrue ( "Incorrect result", actual );
// equal to another engine with the same force
a = new AbstractEngine( 19 ) { };
b = new AbstractEngine( 19 ) { };
actual = a.equals( b );
assertTrue ( "Incorrect result", actual );
// not equal to another engine with a different force
a = new AbstractEngine( 22 ) { };
b = new AbstractEngine( 24 ) { };
actual = a.equals( b );
assertFalse( "Incorrect result", actual );
// not equal to null
actual = a.equals( null );
assertFalse( "Incorrect result", actual );
// not equal to some other object
actual = a.equals( "22" );
assertFalse( "Incorrect result", actual );
// not equal to some other object
actual = a.equals( 22 );
assertFalse( "Incorrect result", actual );
}
@Test
public void test3_AbstractEngineHasCompareTo() {
Engine a, b;
int actual;
// equal to itself
a = new AbstractEngine( 42 ) { };
actual = a.compareTo( a );
assertTrue( "Incorrect result", actual == 0 );
// equal to another engine with the same force
a = new AbstractEngine( 9000 ) { };
b = new AbstractEngine( 9000 ) { };
actual = a.compareTo( b );
assertTrue( "Incorrect result", actual == 0 );
// goes before a more powerful engine
a = new AbstractEngine( 23 ) { };
b = new AbstractEngine( 24 ) { };
actual = a.compareTo( b );
assertTrue( "Incorrect result", actual < 0 );
// goes after a less powerful engine
actual = b.compareTo( a );
assertTrue( "Incorrect result", actual > 0 );
}
@Test
public void test4_OxIsAnEngine() {
Ox ox = new Ox( 3 );
assertTrue( "Incorrect result", ox instanceof AbstractEngine );
}
@Test
public void test5_OxHasGetForce() {
Engine engine = new Ox( 4 );
int actual = engine.getForce();
int expected = 4;
assertEquals( "Incorrect result", expected, actual );
}
@Test
public void test5_OxHasEquals() {
Engine a, b;
boolean actual;
// equal to itself
a = new Ox( 42 );
actual = a.equals( a );
assertTrue ( "Incorrect result", actual );
// equal to another engine with the same force
a = new Ox( 19 );
b = new Ox( 19 );
actual = a.equals( b );
assertTrue ( "Incorrect result", actual );
// not equal to another engine with a different force
a = new Ox( 22 );
b = new Ox( 24 );
actual = a.equals( b );
assertFalse( "Incorrect result", actual );
// not equal to another engine of equal force
a = new Ox ( 21 );
b = new AbstractEngine( 21 ) { };
actual = a.equals( b );
assertFalse( "Incorrect result", actual );
// not equal to null
actual = a.equals( null );
assertFalse( "Incorrect result", actual );
// not equal to some other object
actual = a.equals( "blah" );
assertFalse( "Incorrect result", actual );
// not equal to some other object
actual = a.equals( 111 );
assertFalse( "Incorrect result", actual );
}
}
AbstractEngine
, you need to set the force
member variable. AbstractEngine
的构造函数中,您需要设置force
成员变量。 getForce()
method in AbstractClass
, if this method looks exactly the same as in class Engine
. Engine
方法完全相同,则getForce()
在AbstractClass
具有getForce()
方法。 compareTo
method as described in the assignment, either in the Engine
class or in the AbstractEngine
class. Engine
类或AbstractEngine
类中实现分配中所述的compareTo
方法。 Reading the description, shouldn't the force
member variable be in the AbstractEngine
class instead of the Engine
class? 阅读说明,
force
成员变量不应该在AbstractEngine
类而不是Engine
类中吗? (If you put it in AbstractEngine
, then getForce()
should also be in AbstractEngine
instead of Engine
). (如果将其放在
AbstractEngine
,则getForce()
也应该位于AbstractEngine
而不是Engine
)。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.