【ThinkingInJava】46、把数组反序排列

最新推荐文章于 2019-12-09 19:50:34 发布

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本文介绍了一个具体的Java示例，展示了如何使用自定义类CompType实现Comparable接口以支持排序操作，并利用Generated类的方法来生成和填充数组。通过实例演示了数组的创建、随机数据的生成、排序前后数组内容的变化。

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//: net/mindview/util/Generated.java
package net.mindview.util;
import java.util.*;

public class Generated 
{
  // Fill an existing array:
  public static <T> T[] array(T[] a, Generator<T> gen) 
  {
    return new CollectionData<T>(gen, a.length).toArray(a);
  }
  // Create a new array:
  @SuppressWarnings("unchecked")
  public static <T> T[] array(Class<T> type,
      Generator<T> gen, int size) 
  {
    T[] a =
      (T[])java.lang.reflect.Array.newInstance(type, size);
    return new CollectionData<T>(gen, size).toArray(a);
  }
} ///:~

package Lesson16Arrays;

//: arrays/CompType.java
// Implementing Comparable in a class.
import java.util.*;
import net.mindview.util.*;
import static net.mindview.util.Print.*;

public class CompType implements Comparable<CompType> 
{
  int i;
  int j;
  private static int count = 1;	//静态的
  
  public CompType(int n1, int n2) 	//构造函数，给两个私有成员赋值
  {
    i = n1;
    j = n2;
  }
  
  public String toString() 
  {
    String result = "[i = " + i + ", j = " + j + "]";
    
    if(count++ % 3 == 0)	//当个数恰好是3的倍数时候换行，并++，每输出一次就++
      result += "\n";
    return result;
  }
  
  public int compareTo(CompType rv) //sort函数会调用这个
  {
    return (i < rv.i ? -1 : (i == rv.i ? 0 : 1));//要比较的对象的i比这个大的话，就返回-1
  }
  
  private static Random r = new Random(47);	//私有静态的，产生
  
  public static Generator<CompType> generator() 
  {
    return new Generator<CompType>() 
	{
      public CompType next() 
      {
        return new CompType(r.nextInt(100),r.nextInt(100));	//在 0（包括）和指定值（不包括）之间均匀分布的 int 值
      }
    };
  }
  
  public static void main(String[] args) 
  {
    CompType[] a =
      Generated.array(new CompType[12], generator());	//后面那个参数每次调用的时候随机产生数据，用来初始化前面那个对象
    print("before sorting:");
    print(Arrays.toString(a));
    Arrays.sort(a);
    print("after sorting:");
    print(Arrays.toString(a));
  }
}

输出：

before sorting: obj1
[[i = 58, j = 55], [i = 93, j = 61], [i = 61, j = 29]
, [i = 68, j = 0], [i = 22, j = 7], [i = 88, j = 28]
, [i = 51, j = 89], [i = 9, j = 78], [i = 98, j = 61]
, [i = 20, j = 58], [i = 16, j = 40], [i = 11, j = 22]
] obj1
after sorting: obj1
[[i = 98, j = 61], [i = 93, j = 61], [i = 88, j = 28]
, [i = 68, j = 0], [i = 61, j = 29], [i = 58, j = 55]
, [i = 51, j = 89], [i = 22, j = 7], [i = 20, j = 58]
, [i = 16, j = 40], [i = 11, j = 22], [i = 9, j = 78]
] obj1