知识点
1.数组可以直接排序，不用转换为ArrayList。
java.util.Arrays.sort(T[] a, Comparator<? super T> c)
2.利用Comparator接口，我们可以方便的设计自己的排序规则。
Comparator接口里就一个函数，int compare(T o1, T o2)
返回值有三个， 0， -1， 1
分别表示，相等，小于和大于
3.中文字符串如何排序
中文字符串排序肯定要用到中文排序的Comparator，幸运的是，java有提供这样的Comparator。
获取方法
Collator.getInstance(java.util.Locale.CHINA);
下面是，自己封装的一个文件排序的类，有四种排序方法。
package com.test;
import java.io.File;
import java.sql.Date;
import java.text.Collator;
import java.util.Arrays;
import java.util.Comparator;
public class FileSorter implements Comparator<File>{
/**默认排序的方式， 按目录，文件排序TYPE_DIR*/
public static final int TYPE_DEFAULT = -1;
/**按修改时间，降序*/
public static final int TYPE_MODIFIED_DATE_DOWN = 1;
/**按修改时间，升序*/
public static final int TYPE_MODIFIED_DATE_UP = 2;
/**按文件大小，降序*/
public static final int TYPE_SIZE_DOWN = 3;
/**按文件大小，升序*/
public static final int TYPE_SIZE_UP = 4;
/* public static final int TYPE_NAME_DOWN = 5;
public static final int TYPE_NAME_UP = 6;*/
/**按文件名*/
public static final int TYPE_NAME = 5;
/**按目录，文件排序*/
public static final int TYPE_DIR = 7;
private int mType = -1;
public FileSorter(int type) {
if (type < 0 || type > 7) {
type = TYPE_DIR;
}
mType = type;
}
@Override
public int compare(File object1, File object2) {
int result = 0;
switch (mType) {
case TYPE_MODIFIED_DATE_DOWN://last modified date down
result = compareByModifiedDateDown(object1, object2);
break;
case TYPE_MODIFIED_DATE_UP://last modified date up
result = compareByModifiedDateUp(object1, object2);
break;
case TYPE_SIZE_DOWN: // file size down
result = compareBySizeDown(object1, object2);
break;
case TYPE_SIZE_UP: //file size up
result = compareBySizeUp(object1, object2);
break;
case TYPE_NAME: //name
result = compareByName(object1, object2);
break;
case TYPE_DIR: //dir or file
result = compareByDir(object1, object2);
break;
default:
result = compareByDir(object1, object2);
break;
}
return result;
}
private int compareByModifiedDateDown(File object1, File object2) {
long d1 = object1.lastModified();
long d2 = object2.lastModified();
if (d1 == d2){
return 0;
} else {
return d1 < d2 ? 1 : -1;
}
}
private int compareByModifiedDateUp(File object1, File object2) {
long d1 = object1.lastModified();
long d2 = object2.lastModified();
if (d1 == d2){
return 0;
} else {
return d1 > d2 ? 1 : -1;
}
}
private int compareBySizeDown(File object1, File object2) {
if (object1.isDirectory() && object2.isDirectory()) {
return 0;
}
if (object1.isDirectory() && object2.isFile()) {
return -1;
}
if (object1.isFile() && object2.isDirectory()) {
return 1;
}
long s1 = object1.length();
long s2 = object2.length();
if (s1 == s2){
return 0;
} else {
return s1 < s2 ? 1 : -1;
}
}
private int compareBySizeUp(File object1, File object2) {
if (object1.isDirectory() && object2.isDirectory()) {
return 0;
}
if (object1.isDirectory() && object2.isFile()) {
return -1;
}
if (object1.isFile() && object2.isDirectory()) {
return 1;
}
long s1 = object1.length();
long s2 = object2.length();
if (s1 == s2){
return 0;
} else {
return s1 > s2 ? 1 : -1;
}
}
private int compareByName(File object1, File object2) {
Comparator<Object> cmp = Collator.getInstance(java.util.Locale.CHINA);
return cmp.compare(object1.getName(), object2.getName());
}
private int compareByDir(File object1, File object2) {
if (object1.isDirectory() && object2.isFile()) {
return -1;
} else if (object1.isDirectory() && object2.isDirectory()) {
return compareByName(object1, object2);
} else if (object1.isFile() && object2.isDirectory()) {
return 1;
} else { //object1.isFile() && object2.isFile())
return compareByName(object1, object2);
}
}
//for test
public static void main(String[] args){
File[] list = new File("/usr").listFiles();
Arrays.sort(list, new FileSorter(FileSorter.TYPE_SIZE_UP));
printFileArray(list);
}
//for test
private static void printFileArray(File[] list) {
System.out.println("文件大小\t\t文件修改日期\t\t文件类型\t\t文件名称");
for (File f : list) {
System.out.println(f.length() + "\t\t" + new Date(f.lastModified()).toString() + "\t\t" + (f.isDirectory() ? "目录" : "文件") + "\t\t" + f.getName() );
}
}
}