java - java中如何扩展抽象类

Question

我制作了一个引擎类，如下所示。基于

Engine:扩展Java的Comparable(在引擎之间进行比较)并声明一个整数的接口(interface)getter 方法“getForce”，表示引擎子类将拥有它们能够承受的力量
生产。

public interface Engine extends Comparable<Engine>{

public int getForce();

}

我正在尝试根据以下描述创建一个 AbstractEngine 类。

AbstractEngine:大多数引擎实现的抽象类。它是 Engine 的子类，并有一个指示其力量的整数字段。该字段通过构造函数初始化。该类重写了 Engine 中的 getForce 和 Comparable 中的 compareTo。两个引擎的比较是通过查找它们的力量之间的差异来完成的(以对引擎集合进行排序的方式进行排列)。我对覆盖 Engine 中的方法并确保 AbstractEngine 与 Engine 进行比较感到困惑。

这就是我目前所拥有的，但它无法通过 JUnit 测试检查 AbstractEngine 是否具有 getForce、equals 和 CompareTo。我是否有特定的方法来扩展这些方法？

abstract class AbstractEngine implements Engine {

public AbstractEngine(int force){

}
public int compareTo(Engine o) {
    // TODO Auto-generated method stub
    return 0;
}
}

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 );
}
}

Answer 1

• 在AbstractEngine的构造函数中，需要设置force成员变量。
• 如果 AbstractClass 中的 getForce() 方法看起来与类 Engine 中的完全相同，则无需在该方法中使用 getForce() 方法。
• 您必须按照作业中的描述，在 Engine 类或 AbstractEngine 类中实现 compareTo 方法。

读了描述，force成员变量不应该在AbstractEngine类中而不是在Engine类中吗？ (如果将其放入 AbstractEngine 中，则 getForce() 也应该位于 AbstractEngine 中，而不是 Engine 中)。