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现在，我们要对对象实例进行比较。既然是对象比较，那么比较的规则不尽相同。比较规则不同，那么我们就可以对不同的东西设置一个接口，在这里也就是将比较规则放到一个Comparable的接口中，实现其中的compareTo方法就得到给出具体比较规则的结果。这也就意味着，要进行比较的对象，都得首先实现这个接口。
1 package program.strategy.model; 2 3 public interface Comparable { 4 public int compareTo(Object o); 5 } 6 7 8 9 public class Cat implements Comparable{ 10 11 private int id; 12 private int weight; 13 14 public Cat(int id,int weight) { 15 this.id=id; 16 this.weight=weight; 17 } 18 @Override 19 public int compareTo(Object o) { 20 if(o instanceof Cat) { 21 Cat c=(Cat)o; 22 if(this.weight>c.weight) { 23 return 1; 24 }else if(this.weight<c.weight) { 25 return -1; 26 } 27 return 0; 28 } 29 throw new RuntimeException("对象类型不正确"); 30 } 31 32 public String toString() { 33 return "cat"+id+"_weight"+weight; 34 } 35 public int getId() { 36 return id; 37 } 38 public void setId(int id) { 39 this.id = id; 40 } 41 public int getWeight() { 42 return weight; 43 } 44 public void setWeight(int weight) { 45 this.weight = weight; 46 } 47 48 49 50 public class Dog implements Comparable{ 51 private int id; 52 private int weight; 53 public Dog(int id,int weight) { 54 this.id=id; 55 this.weight=weight; 56 } 57 58 @Override 59 public int compareTo(Object o) { 60 if(o instanceof Dog) { 61 Dog d=(Dog)o; 62 if(this.weight>d.weight) { 63 return 1; 64 }else if(this.weight<d.weight) { 65 return -1; 66 } 67 return 0; 68 } 69 throw new RuntimeException("类型比较错误"); 70 } 71 72 public String toString() { 73 return "dog"+id+"_weight"+weight; 74 } 75 76 public int getId() { 77 return id; 78 } 79 80 public void setId(int id) { 81 this.id = id; 82 } 83 84 public int getWeight() { 85 return weight; 86 } 87 88 public void setWeight(int weight) { 89 this.weight = weight; 90 } 91 } 92 93 94 95 public class DataSorter { 96 public static void sort(Object[] objs) { 97 int len=objs.length; 98 for(int i=len-1;i>0;i--) { 99 Comparable o1=(Comparable)objs[i]; 100 for(int j=0;j<i;j++) { 101 Comparable o2=(Comparable)objs[j]; 102 if(o1.compareTo(o2)<0) { 103 Object o=objs[j]; 104 objs[j]=objs[i]; 105 objs[i]=o; 106 } 107 } 108 } 109 } 110 } 111 112 113 114 public class Main { 115 public static void main(String[]args) { 116 Dog[] dogs=new Dog[]{new Dog(1,2),new Dog(2,34),new Dog(3,4)}; 117 DataSorter.sort(dogs); 118 for(Dog d:dogs) { 119 System.out.println(d); 120 } 121 } 122 }
评价：上面的类，就DataSorter就相当于是类库提供的，它提供了排序的算法。我们只要给对象提供比较的规则，当然就可以对对象进行排序。但是，除了DataSorter，其他所有的类对比较的实体类都存在依赖性，这也就意味着，如果改变比较的规则，要修改的地方是挺多的。上面的接口只是提供了一种提供比较规则的方法，现在，我们可以对于可能将来会发生变化的比较规则再提供一个接口Comparator。
1 package program.strategy.model; 2 3 public interface Comparator { 4 public int compare(Object o1,Object o2); 5 } 6 7 8 9 public class WeightComparator implements Comparator{ 10 @Override 11 public int compare(Object o1, Object o2) { 12 Cat c1=(Cat)o1; 13 Cat c2=(Cat)o2; 14 if(c1.getWeight()>c2.getWeight()) { 15 return 1; 16 }else if(c1.getWeight()<c2.getWeight()) { 17 return -1; 18 } 19 return 0; 20 } 21 22 } 23 24 25 26 public class Cat implements Comparable{ 27 private int id; 28 private int weight; 29 private Comparator comparator=new WeightComparator(); 30 31 public Cat(int id,int weight) { 32 this.id=id; 33 this.weight=weight; 34 } 35 @Override 36 public int compareTo(Object o) { 37 return comparator.compare(this, o); 38 } 39 40 public String toString() { 41 return "cat"+id+"_weight"+weight; 42 } 43 public int getId() { 44 return id; 45 } 46 public void setId(int id) { 47 this.id = id; 48 } 49 public int getWeight() { 50 return weight; 51 } 52 public void setWeight(int weight) { 53 this.weight = weight; 54 } 55 }
这样，通过添加一个比较规则类WeightComparator从而降低了各个类与具体比较规则的耦合度。因为，它将这种关联都放到了WeightComparator当中；如果我们以后要对身高进行比较，就可以添加比较规则类HeightComparator即可。另外，该具体类当中比较规则的实例化。
标签：style blog class code java color
原文地址：http://www.cnblogs.com/feijishuo/p/3705344.html
