与遗产有关的家庭作业
问题描述:
问候。除了一项要求外,我已经完成了一所学校的项目。与遗产有关的家庭作业
的要求是:
注意,SeaCreature类定义了不同方向的四个常数。确保使用它们。尽管您可能会认为它们始终是int类型,但您的代码不应该依赖于分配给这些常量的特定值。
我看不到这个值。分配的常量值是逻辑上的,并且可以方便地使用随机返回方向。如果分配的值是四个非连续的数字,这会使代码真的变得复杂。
下面是在作业中提到的原始SeaCreature类,然后是我的一个使用Random的生物的代码。除了在每个类别中涉及随机移动的NORTH,SOUTH,EAST,WEST分配新值之外,是否有更清晰的方法来返回基本方向而不是0-3的值?
非常感谢您的建议,并请询问是否需要澄清。
import java.util.*;
/**
* Defines the attributes and behaviors common to all SeaCreatures in order to participate
* in the SeaCreature simulation.
*
* Each SeaCreature is represented by a char.
* Each SeaCreature can answer back its char when asked.
* Each SeaCreature can answer its next move, NORTH, SOUTH, EAST, WEST.
*
*/
public abstract class SeaCreature {
private char ch;
/** defined constant to facilitate random movement*/
public static final Random rand = new Random();
/** defined constant to move one unit NORTH */
public static final int NORTH = 0;
/** defined constant to move one unit SOUTH */
public static final int SOUTH = 1;
/** defined constant to move one unit EAST */
public static final int EAST = 2;
/** defined constant to move one unit WEST */
public static final int WEST = 3;
/**
* Construct a SeaCreature object with the given character representation
* @param c the character for this SeaCreature
*/
public SeaCreature (char c){
ch = c;
}
/**
* Answers back the character representation for this SeaCreature
* @return this SeaCreature's initial
*/
public char getChar(){
return ch;
}
/** Answers back the next move for this SeaCreature.
* Must be overridden by subclasses
* @return NORTH, SOUTH, EAST, or WEST
*/
public abstract int getMove();
}
我的海狮类:
/**
* Defines the attributes and behaviors specific to SeaLions in order to participate
* in the SeaCreature simulation.
*
* @author Justin Ashburn
* @version 6/5/2011
*/
public class SeaLion extends SeaCreature {
/** defined char to represent a SeaLion*/
private static final char SEALION = 'L';
/** defined steps before SeaLion cycle repeats*/
private static final int CYCLE_LENGTH = 3;
/** defined steps before SeaLion's first direction*/
private static final int DIRECTION_ONE_LENGTH = 2;
private int directionOne;
private int count;
/**
* Construct a SeaLion object with the given character representation
*/
public SeaLion(){
super(SEALION);
// establishes an initial direction
directionOne = rand.nextInt(4);
count = 0;
}
/** Moves like the 'Knight' chess piece. ie. Picks a random direction, moves 2 times
* in that direction, and then randomly chooses a direction perpendicular to the first
* and moves in that direction once.
*
* @return 0, 1, 2, or 3
*/
public int getMove() {
int direction;
int directionTwo;
// continues with direction one for the appropriate length
if (count < DIRECTION_ONE_LENGTH) {
count ++;
direction = directionOne;
}
// if directionOne was east or west chooses a new north or south direction for last move
else if (count < CYCLE_LENGTH && directionOne > 1) {
directionTwo = rand.nextInt(2);
direction = directionTwo;
// resets count and establishes new direction in next cycle
count = 0;
directionOne = rand.nextInt(4);
}
// if directionOne was north or south chooses a new east or west direction for last move
else {
directionTwo = rand.nextInt(2) + 2;
direction = directionTwo;
// resets count and establishes new direction in next cycle
count = 0;
directionOne = rand.nextInt(4);
}
return direction;
}
}
答
我想我会做这样的事情:
private static final int AXES[][] = {
{NORTH,SOUTH},
{EAST,WEST}
};
...
private int directionOne;
private int directionTwo;
private int count;
...
public SeaLion(){
super(SEALION);
// establishes an initial direction
nextCycle();
}
...
public int getMove() {
int direction;
if (count < DIRECTION_ONE_LENGTH) {
direction = directionOne;
} else {
direction = directionTwo;
}
++count;
if (count == CYCLE_LENGTH) {
nextCycle();
}
return direction;
}
...
private void nextCycle() {
int axis1 = random.nextInt(2);
int axis2 = 1 - axis1;
directionOne = AXES[axis1][random.nextInt(2)];
directionTwo = AXES[axis2][random.nextInt(2)];
count = 0;
}
答
您可以让NORTH
,SOUTH
,WEST
,并且EAST
是任一方向或标题,如下:
标题:
public static final int NORTH = 0;
public static final int SOUTH = 180;
public static final int EAST = 90;
public static final int WEST = 270; // Or -90
方位:
public static final int NORTH = 90;
public static final int SOUTH = 270; // Or -90
public static final int EAST = 0;
public static final int WEST = 180;
答
您需要的是从0到3之间的整数到4个已命名常量的值的简单映射......而不对这些值做出任何假设。
你怎么能实现呢?提示:什么简单的Java数据结构从(从零到长度 - 1)映射到其他东西?
我不明白这与继承有什么关系,除了'extends'关键字的存在。 – 2011-06-07 04:22:47
SeaLion延伸SeaCreature。这是继承。 – Nik 2011-06-07 04:23:40
我看不到你在代码中使用'const'的地方。是的,你使用的是int值,但不是const。我*认为*这就是要求所要求的。在这种特殊情况下没有太多价值,因为这是一个简单的概念。但是你的下一个项目可能是那些'常量不那么简单 - 也许他们是字符串 - 你怎么做到随机1-4?在这种情况下,你应该很容易编写一个GetRandomDirection()方法,该方法返回一个INT,并且可以从const中随机选取? – Prescott 2011-06-07 04:35:15