Arrays.sort()使用方法

今天在做一个按更新时间搜寻出某个文件夹里面的所有文件，由于自己写算法比较花费时间，干脆就用j2se提供的类Arrays提供的sort（）方法，这样就比较省力。对于基本数据类型只要Arrays.sort(数组)[“注：数组是声明为基本数据类型的数组，如int[]等”]对于对象类型，要 implement Comparable，所以得重载 compareTo() 这个方法。有了这个方法，那么 Arrays.sort() 就能依照这个方法的回传值来作排序的依据。事实上，基本数据类型也都有 implement Comparable 的，所以才能够这样子使用。一般而言，我们习惯的排序结果是由小到大，所以在 compareTo() 当中「大于」是回传正值，如果你希望得到的结果是由大到小，那么只要 return 的部分改一下，也就可以了。不过不建议这样子作，会降低程序可读性；况且，只要把数组逆向 traversal 不就得到一样的结果啦...import java.util.Arrays;
import java.util.Comparator;public class ArraySortDemo {/**
* 整数型数组排序
*/public void sortIntArray() {int[] arrayToSort = new int[] { 48, 5, 89, 80, 81, 23, 45, 16, 2 };System.out.println("整数型数组排序,排序前:");for (int i = 0; i < arrayToSort.length; i++){System.out.print(arrayToSort[i]+",");}// 调用数组的静态排序方法sortArrays.sort(arrayToSort);System.out.println();System.out.println("排序后:");for (int i = 0; i < arrayToSort.length; i++){System.out.print(arrayToSort[i]+",");}}/**
* 字符型数组排序demo
*/public void sortStringArray() {String[] arrayToSort = new String[] { "Oscar", "Charlie", "Ryan","Adam", "David","aff","Aff" };System.out.println();System.out.println("字符型数组排序,排序前:");for (int i = 0; i < arrayToSort.length; i++){System.out.print(arrayToSort[i]+",");}System.out.println();System.out.println("排序后:");// 调用数组的静态排序方法sortArrays.sort(arrayToSort);for (int i = 0; i < arrayToSort.length; i++){System.out.print(arrayToSort[i]+",");}}/**
* 对象数组排序demo
*/public void sortObjectArray() {Dog o1 = new Dog("dog1", 1);Dog o2 = new Dog("dog2", 4);Dog o3 = new Dog("dog3", 5);Dog o4 = new Dog("dog4", 2);Dog o5 = new Dog("dog5", 3);Dog[] dogs = new Dog[] { o1, o2, o3, o4, o5 };System.out.println();System.out.println("对象数组排序排序前:");for (int i = 0; i < dogs.length; i++) {Dog dog = dogs[i];System.out.print(dog.getName()+"["+dog.getWeight()+"],");}Arrays.sort(dogs, new ByWeightComparator());System.out.println();System.out.println("排序后：");for (int i = 0; i < dogs.length; i++) {Dog dog = dogs[i];System.out.print(dog.getName()+"["+dog.getWeight()+"],");}}public static void main(String[] args) {ArraySortDemo t = new ArraySortDemo();t.sortIntArray();t.sortStringArray();t.sortObjectArray();}}/**
* 定义了一个Dog类
*/class Dog {
private String name;
private int weight;public Dog(String name, int weight) {this.setName(name);this.weight = weight;
}public int getWeight() {return weight;
}public void setWeight(int weight) {this.weight = weight;
}public void setName(String name) {this.name = name;
}public String getName() {return name;
}
}/**
* 因为要对对象进行排序，所以要实现java.util.Comparator接口的compare(T o1, T o2)方法，在该方法中自定义排序算法。
*/class ByWeightComparator implements Comparator {
public final int compare(Object pFirst, Object pSecond) {int aFirstWeight = ((Dog) pFirst).getWeight();int aSecondWeight = ((Dog) pSecond).getWeight();int diff = aFirstWeight - aSecondWeight;if (diff > 0)return 1;if (diff < 0)return -1;elsereturn 0;
}
}运行结果：整数型数组排序,排序前:
48,5,89,80,81,23,45,16,2
排序后:
2,5,16,23,45,48,80,81,89
字符型数组排序,排序前:
Oscar,Charlie,Ryan,Adam,David,aff,Aff
排序后:
Adam,Aff,Charlie,David,Oscar,Ryan,aff
对象数组排序排序前:
dog1[1],dog2[4],dog3[5],dog4[2],dog5[3]
排序后：
dog1[1],dog4[2],dog5[3],dog2[4],dog3[5]