i 类 Shape 具有一个私有字段 shapeColor，类 Triangle 、 Rectangle 和 Circle 扩展了 Shape 并拥有自己的其他字段。 我写了Shape的比较方法。 （我需要按颜色名称对它们进行排序）
public int compare (Shape obj) {
return (this.getShapeColor().compareTo(obj.getShapeColor()));
}
在 psvm 的主类中我有下一个代码：
Shape[] arr3 = new Shape[10];
arr3[6] = new Rectangle("RED", 11, 22);
arr3[1] = new Rectangle("GREEN", 12, 23);
arr3[7] = new Rectangle("BLACK", 13, 24);
arr3[3] = new Rectangle("YELLOW", 14, 25);
arr3[4] = new Rectangle("WHITE", 15, 26);
arr3[5] = new Circle("BLUE", 4);
arr3[0] = new Circle("BROWN", 5);
arr3[2] = new Triangle("BROWN", 5, 3, 4);
arr3[8] = new Triangle("ROYAL BLUE", 5, 7, 8);
arr3[9] = new Triangle("CHILD'S SURPRISE", 6, 4, 6);
Arrays.sort(arr3, Shape::compare);
问题是 Shape 类在我的任务中必须是抽象的，但是 Arrays.sort(arr3, Shape::compare);没用。我该如何解决这个问题？
我建议这样一个形状的抽象基类：
public abstract class Shape implements Comparable<Shape> {
private String color;
public Shape(String color) {
super();
this.color = color;
}
// geters & setters
@Override
public int compareTo(Shape other) {
if ((getAsciiSum(this.color)).compareTo(getAsciiSum(other.color)) < 0) {
return -1;
}
if ((getAsciiSum(this.color)).compareTo(getAsciiSum(other.color)) == 0) {
return 0;
}
return 1;
}
// toString
public int getAsciiSum() {
return getAsciiSum(this.color);
}
private Integer getAsciiSum(String str) {
int sum = 0;
for (Character ch : str.toCharArray()) {
int asciiValue = ch;
sum += asciiValue;
}
return sum;
}
// finish
形状扩展器可以如下
圆圈：
public class Circle extends Shape implements ShapeType {
private int radius;
public Circle(String color) {
super(color);
}
public Circle(String color, int radius) {
this(color);
this.radius = radius;
}
// geters & setters, toString
矩形：
public class Rectangle extends Shape implements ShapeType {
int width;
int highth;
public Rectangle(String color) {
super(color);
}
public Rectangle(String color, int width, int highth) {
this(color);
this.width = width;
this.highth = highth;
}
// geters & setters, toString
三角形：
public class Triangle extends Shape implements ShapeType {
private int sideOne;
private int sideTwo;
private int sideThree;
public Triangle(String color) {
super(color);
}
public Triangle(String color, int sideOne, int sideTwo, int sideThree) {
this(color);
this.sideOne = sideOne;
this.sideTwo = sideTwo;
this.sideThree = sideThree;
}
// geters & setters, toString
并执行以下命令后：
System.out.println("\nbefore sort:");
print(arr3);
Arrays.sort(arr3, Shape::compareTo);
System.out.println("\nafter sort:");
print(arr3);
我们可以获得结果 -
排序前：
Circle [AsciiSum=392, color=BROWN, radius=5]|i=0
Rectangle [AsciiSum=369, color=GREEN, width=12, highth=23]|i=1
Triangle [AsciiSum=392, color=BROWN, sideOne=5, sideTwo=3, sideThree=4]|i=2
Rectangle [AsciiSum=476, color=YELLOW, width=14, highth=25]|i=3
Rectangle [AsciiSum=385, color=WHITE, width=15, highth=26]|i=4
Circle [AsciiSum=296, color=BLUE, radius=4]|i=5
Rectangle [AsciiSum=219, color=RED, width=11, highth=22]|i=6
Rectangle [AsciiSum=349, color=BLACK, width=13, highth=24]|i=7
Triangle [AsciiSum=719, color=ROYAL BLUE, sideOne=5, sideTwo=7, sideThree=8]|i=8
Triangle [AsciiSum=1147, color=CHILDS SURPRISE, sideOne=6, sideTwo=4, sideThree=6]|i=9
排序后：
Rectangle [AsciiSum=219, color=RED, width=11, highth=22]|i=0
Circle [AsciiSum=296, color=BLUE, radius=4]|i=1
Rectangle [AsciiSum=349, color=BLACK, width=13, highth=24]|i=2
Rectangle [AsciiSum=369, color=GREEN, width=12, highth=23]|i=3
Rectangle [AsciiSum=385, color=WHITE, width=15, highth=26]|i=4
Circle [AsciiSum=392, color=BROWN, radius=5]|i=5
Triangle [AsciiSum=392, color=BROWN, sideOne=5, sideTwo=3, sideThree=4]|i=6
Rectangle [AsciiSum=476, color=YELLOW, width=14, highth=25]|i=7
Triangle [AsciiSum=719, color=ROYAL BLUE, sideOne=5, sideTwo=7, sideThree=8]|i=8
Triangle [AsciiSum=1147, color=CHILD'S SURPRISE, sideOne=6, sideTwo=4, sideThree=6]|i=9
-- 编辑 --
当然，颜色字段中的字符串可以按字典顺序进行比较，然后compareTo方法就可以很简单，如：
@Override
public int compareTo(Shape other) {
if ((this.color).compareTo(other.color) < 0) {
return -1;
}
if ((this.color).compareTo(other.color) == 0) {
return 0;
}
return 1;
}
排序后数组元素的顺序如下：
Rectangle [AsciiSum=349, color=BLACK, width=13, highth=24]|i=0
Circle [AsciiSum=296, color=BLUE, radius=4]|i=1
Circle [AsciiSum=392, color=BROWN, radius=5]|i=2
Triangle [AsciiSum=392, color=BROWN, sideOne=5, sideTwo=3, sideThree=4]|i=3
Triangle [AsciiSum=1147, color=CHILD'S SURPRISE, sideOne=6, sideTwo=4, sideThree=6]|i=4
Rectangle [AsciiSum=369, color=GREEN, width=12, highth=23]|i=5
Rectangle [AsciiSum=219, color=RED, width=11, highth=22]|i=6
Triangle [AsciiSum=719, color=ROYAL BLUE, sideOne=5, sideTwo=7, sideThree=8]|i=7
Rectangle [AsciiSum=385, color=WHITE, width=15, highth=26]|i=8
Rectangle [AsciiSum=476, color=YELLOW, width=14, highth=25]|i=9
Arrays.sort()ComparatorComparatorComparator shapeComparator = new Comparator<Shape>() {
@Override
public int compare(Shape o1, Shape o2) {
return o1.color.compareTo(o2.color);
}
};
你可以像这样将定义的
shapeComparatorArrays.sort()Arrays.sort(shapes, shapeComparator);
Class Shape{
protected String color;
@Override
public int hashCode(){
//give your definition
}
@Override
public int equals(){
//give your definition
}
}
Class Rectangle extends Shape{
private int height;
private int length;
}
Class Circle extends Shape{
private int redius;
}
Class Triangle extends Shape{
//declare your member variable
}
尝试编写一个比较器类并在 Arrays.sort(arr, shapeComparator) 中传递它的引用。
并自动 sort() 方法对形状类数组进行排序。
class SortbyColor implements Comparator<Shape> {
// Used for sorting in ascending order of
// Color
public int compare(Shape a, Shape b)
{
return a.color.compareTo(b.color);
}
}
OR 上面的比较器代码也可以重写为
Comparator shapeComparator = new Comparator<Shape>() {
@Override
public int compare(Shape a, Shape b) {
return a.color.compareTo(b.color);
}
};
现在调用
Arrays.sort(arr, new SortbyColor())