今天在做一个按更新时间搜寻出某个目录里面的全部文件，因为自己写算法比較花费时间，干脆就用j2se提供的类Arrays提供的sort（）方法，这样就比較省力。对于基本数据类型仅仅要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() 就能按照这种方法的回传值来作排序的根据。其实，基本数据类型也都有 implement Comparable 的，所以才可以这样子使用。一般而言，我们习惯的排序结果是由小到大，所以在 compareTo() 其中「大于」是回传正值，假设你希望得到的结果是由大到小，那么仅仅要 return 的部分改一下，也就行了。只是不建议这样子作，会减少程序可读性；况且，仅仅要把数组逆向 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sort
Arrays.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sort
Arrays.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;
}
}
/**
* 由于要对对象进行排序，所以要实现java.util.Comparator接口的compare(T o1, T o2)方法，在该方法中自己定义排序算法。
*/
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;
else
return 0;
}
}
执行结果：
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]