[Java] 03 String获取文件后缀名，判断文件是否合法

package test.string;

import java.util.Arrays;
import java.util.List;

public class GetFileType {
    private static List<String> accTypes = Arrays.asList("jpg","bmp","gif","doc","docx","rar");
    public static void main(String[] args){
        for(String arg:args){
            String type = getFileType(arg);
            if(accTypes.contains(type)){
                System.out.println(arg+"后缀合法");
            }else{
                System.out.println(arg+"后缀不合法");
            }
        }
    }
    /**
     * 获取文件后缀名
     * @param filename
     * @return
     */
    public static String getFileType(String filename){
        int pos = filename.lastIndexOf(".");
        if(pos == -1){
            return null;
        }
        return filename.substring(pos+1);
    }
}