java Arrays类应用

 1 package arrays;
 2 
 3 import java.util.Arrays;
 4 import java.util.Comparator;
 5 
 6 public class ArraysExercise01 {
 7     public static void main(String[] args) {
 8         Book[]books=new  Book[4];
 9         books[0]=new Book("红楼梦",100);
10         books[1]=new Book("水浒传",90);
11         books[2]=new Book("青年文摘",5);
12         books[3]=new Book("java从入门到放弃",300);
13 
14         Arrays.sort(books, new Comparator() {
15             @Override
16             public int compare(Object o1, Object o2) {
17                 if (!(o1 instanceof Book)||!(o2 instanceof Book)){
18                     return 0;
19                 }
20                 Book b1=(Book)o1;
21                 Book b2=(Book)o2;
22                 //返回的正数还是负数，会影响排序的顺序
23                 if(b1.getPrice()-b2.getPrice()>0){
24                     return 1;
25                 }else if (b1.getPrice()-b2.getPrice()<0){
26                     return -1;
27                 }else{
28                     return 0;
29                 }
30 
31             }
32         });
33 
34         System.out.println(Arrays.toString(books));
35     }
36 }
37 class Book{
38     private String name;
39     private double price;
40 
41     public Book(String name, double price) {
42         this.name = name;
43         this.price = price;
44     }
45 
46     public String getName() {
47         return name;
48     }
49 
50     public void setName(String name) {
51         this.name = name;
52     }
53 
54     public double getPrice() {
55         return price;
56     }
57 
58     public void setPrice(double price) {
59         this.price = price;
60     }
61 
62     @Override
63     public String toString() {
64        return "Book[name="+name+",price="+price+"]
";
65     }
66 }

结果：

[Book[name=青年文摘,price=5.0]
, Book[name=水浒传,price=90.0]
, Book[name=红楼梦,price=100.0]
, Book[name=java从入门到放弃,price=300.0]
]

1.上面的为实现Comparator接口匿名类，也成为定制排序

2.下面的是让Book实现Comparable接口，完成排序，也成为自然排序

 1 package arrays;
 2 
 3 import java.util.Arrays;
 4 import java.util.Comparator;
 5 
 6 public class ArraysExercise01 {
 7     public static void main(String[] args) {
 8         Book[]books=new  Book[4];
 9         books[0]=new Book("红楼梦",100);
10         books[1]=new Book("水浒传",90);
11         books[2]=new Book("青年文摘",5);
12         books[3]=new Book("java从入门到放弃",300);
13 
14         /*Arrays.sort(books, new Comparator() {
15             @Override
16             public int compare(Object o1, Object o2) {
17                 if (!(o1 instanceof Book)||!(o2 instanceof Book)){
18                     return 0;
19                 }
20                 Book b1=(Book)o1;
21                 Book b2=(Book)o2;
22                 //返回的正数还是负数，会影响排序的顺序
23                 if(b1.getPrice()-b2.getPrice()>0){
24                     return 1;
25                 }else if (b1.getPrice()-b2.getPrice()<0){
26                     return -1;
27                 }else{
28                     return 0;
29                 }
30 
31             }
32         });
33 
34         System.out.println(Arrays.toString(books));*/
35 
36         Arrays.sort(books);
37         System.out.println(Arrays.toString(books));
38 
39     }
40 }
41 class Book implements Comparable{
42     private String name;
43     private double price;
44 
45     public Book(String name, double price) {
46         this.name = name;
47         this.price = price;
48     }
49 
50     public String getName() {
51         return name;
52     }
53 
54     public void setName(String name) {
55         this.name = name;
56     }
57 
58     public double getPrice() {
59         return price;
60     }
61 
62     public void setPrice(double price) {
63         this.price = price;
64     }
65 
66     @Override
67     public String toString() {
68        return "Book[name="+name+",price="+price+"]
";
69     }
70 
71     @Override
72     public int compareTo(Object o) {
73         if (!(o instanceof Book)){
74             return 0;
75         }
76         Book book=(Book)o;
77         if (this.getPrice()>book.getPrice()){
78             return 1;
79         }else if(this.getPrice()>this.getPrice()){
80             return 1;
81         }else{
82             return 0;
83         }
84 
85     }
86 }

结果：

[Book[name=红楼梦,price=100.0]
, Book[name=水浒传,price=90.0]
, Book[name=青年文摘,price=5.0]
, Book[name=java从入门到放弃,price=300.0]
]