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Java开发常用Util工具类-StringUtil、CastUtil、CollectionUtil、ArrayUtil、PropsUtil

字符串工具类

StringUtil.java

package com.***.util;

/**
 * StringUtil
 * @description: 字符串工具类
 **/
public class StringUtil {

    /**
     * 判断是否为空字符串最优代码
     * @param str
     * @return 如果为空,则返回true
     */
    public static boolean isEmpty(String str){
        return str == null || str.trim().length() == 0;
    }

    /**
     * 判断字符串是否非空
     * @param str 如果不为空,则返回true
     * @return
     */
    public static boolean isNotEmpty(String str){
        return !isEmpty(str);
    }
}

数据类型转换类

CastUtil.java

package com.***.util;

/**
 * CastUtil
 * @description: 数据转型工具类
 **/
public class CastUtil {
    /** 
    * @Description: 转为String类型
    * @Param: [obj] 
    * @return: java.lang.String 如果参数为null则转为空字符串
    */ 
    public static String castString(Object obj){
        return CastUtil.castString(obj,"");
    }

    /** 
    * @Description: 转为String类型(提供默认值)
    * @Param: [obj, defaultValue] 将obj转为string,如果obj为null则返回default
    * @return: String
    */ 
    public static String castString(Object obj,String defaultValue){
        return obj!=null?String.valueOf(obj):defaultValue;
    }

    /** 
    * @Description: 转为double类型,如果为null或者空字符串或者格式不对则返回0
    * @Param: [obj] 
    * @return: String
    */ 
    public static double castDouble(Object obj){
        return CastUtil.castDouble(obj,0);
    }

    /** 
    * @Description: 转为double类型 ,如果obj为null或者空字符串或者格式不对则返回defaultValue
    * @Param: [obj, defaultValue] 
    * @return: String obj为null或者空字符串或者格式不对返回defaultValue
    */ 
    public static double castDouble(Object obj,double defaultValue){
        double value = defaultValue;  //声明结果,把默认值赋给结果
        if (obj!=null){   //判断是否为null
            String strValue = castString(obj);  //转换为String
            if (StringUtil.isNotEmpty(strValue)){   //判断字符串是否为空(是否为空只能判断字符串,不能判断Object)
                try{
                    value = Double.parseDouble(strValue);  //不为空则把值赋给value
                }catch (NumberFormatException e){
                    value = defaultValue;  //格式不对把默认值赋给value
                }

            }
        }
        return value;
    }

    /**
     * 转为long型,如果obj为null或者空字符串或者格式不对则返回0
     * @param obj
     * @return
     */
    public static long castLong(Object obj){
        return CastUtil.castLong(obj,0);
    }

    /**
     * 转为long型(提供默认数值),如果obj为null或者空字符串或者格式不对则返回defaultValue
     * @param obj
     * @param defaultValue
     * @return obj为null或者空字符串或者格式不对返回defaultValue
     */
    public static long castLong(Object obj,long defaultValue){
        long value = defaultValue;  //声明结果,把默认值赋给结果
        if (obj!=null){   //判断是否为null
            String strValue = castString(obj);  //转换为String
            if (StringUtil.isNotEmpty(strValue)){   //判断字符串是否为空(是否为空只能判断字符串,不能判断Object)
                try{
                    value = Long.parseLong(strValue);  //不为空则把值赋给value
                }catch (NumberFormatException e){
                    value = defaultValue;  //格式不对把默认值赋给value
                }

            }
        }
        return value;
    }

    /**
     * 转为int型
     * @param obj
     * @return 如果obj为null或者空字符串或者格式不对则返回0
     */
    public static int castInt(Object obj){
        return CastUtil.castInt(obj,0);
    }

    /**
     * 转为int型(提供默认值)
     * @param obj
     * @param defaultValue
     * @return 如果obj为null或者空字符串或者格式不对则返回defaultValue
     */
    public static int castInt(Object obj,int defaultValue){
        int value = defaultValue;  //声明结果,把默认值赋给结果
        if (obj!=null){   //判断是否为null
            String strValue = castString(obj);  //转换为String
            if (StringUtil.isNotEmpty(strValue)){   //判断字符串是否为空(是否为空只能判断字符串,不能判断Object)
                try{
                    value = Integer.parseInt(strValue);  //不为空则把值赋给value
                }catch (NumberFormatException e){
                    value = defaultValue;  //格式不对把默认值赋给value
                }

            }
        }
        return value;
    }

    /**
     * 转为boolean型,不是true的返回为false
     * @param obj
     * @return
     */
    public static boolean castBoolean(Object obj){
        return CastUtil.castBoolean(obj,false);
    }


    /**
     * 转为boolean型(提供默认值)
     * @param obj
     * @param defaultValue
     * @return
     */
    public static boolean castBoolean(Object obj,boolean defaultValue){
        boolean value = defaultValue;
        if (obj!=null){  //为null则返回默认值
            value = Boolean.parseBoolean(castString(obj));  //底层会把字符串和true对比,所以不用判断是否为空字符串
        }
        return value;
    }
}

集合工具类

CollectionUtil.java

package com.***.util;

import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.MapUtils;
import java.util.Collection;
import java.util.Map;

/**
 * CollectionUtil
 * @description: 集合工具类
 **/
public class CollectionUtil {
    /**
     * 判断collection是否为空
     * @param collection
     * @return
     */
    public static boolean isEmpty(Collection collection){
        //return CollectionUtils.isEmpty(collection);
        return collection == null || collection.isEmpty();
    }

    /**
     * 判断Collection是否非空
     * @return
     */
    public static boolean isNotEmpty(Collection collection){
        return !isEmpty(collection);
    }

    /**
     * 判断map是否为空
     * @param map
     * @return
     */
    public static boolean isEmpty(Map map){
        //return MapUtils.isEmpty(map);
        return map == null || map.isEmpty();
    }

    /**
     * 判断map是否非
     * @param map
     * @return
     */
    public static boolean isNotEmpty(Map map){
        return !isEmpty(map);
    }
}

数组工具类

ArrayUtil.java

/**
 * 数组工具类
 */
public class ArrayUtil {
    /**
     * 判断数组是否为空
     * @param array
     * @return
     */
    public static boolean isNotEmpty(Object[] array){
        return !isEmpty(array);
    }

    /**
     * 判断数组是否非空
     * @param array
     * @return
     */
    public static boolean isEmpty(Object[] array){
        return array==null||array.length==0;
    }
}

Properties文件操作类

PropsUtil.java

package com.***.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * 属性文件工具类
 */
public class PropsUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(PropsUtil.class);

    /**
     * 加载属性文件
     * @param fileName fileName一定要在class下面及java根目录或者resource跟目录下
     * @return
     */
    public static Properties loadProps(String fileName){
        Properties props = new Properties();
        InputStream is = null;
        try {
            //将资源文件加载为流
            is = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName);
props.load(is);
if(is==null){ throw new FileNotFoundException(fileName+"file is not Found"); } } catch (FileNotFoundException e) { LOGGER.error("load properties file filure",e); }finally { if(is !=null){ try { is.close(); } catch (IOException e) { LOGGER.error("close input stream failure",e); } } } return props; } /** * 获取字符型属性(默认值为空字符串) * @param props * @param key * @return */ public static String getString(Properties props,String key){ return getString(props,key,""); } /** * 获取字符型属性(可制定默认值) * @param props * @param key * @param defaultValue 当文件中无此key对应的则返回defaultValue * @return */ public static String getString(Properties props,String key,String defaultValue){ String value = defaultValue; if (props.containsKey(key)){ value = props.getProperty(key); } return value; } /** * 获取数值型属性(默认值为0) * @param props * @param key * @return */ public static int getInt(Properties props,String key){ return getInt(props,key,0); } /** * 获取数值型属性(可指定默认值) * @param props * @param key * @param defaultValue * @return */ public static int getInt(Properties props,String key,int defaultValue){ int value = defaultValue; if (props.containsKey(key)){ value = CastUtil.castInt(props.getProperty(key)); } return value; } /** * 获取布尔型属性(默认值为false) * @param props * @param key * @return */ public static boolean getBoolean(Properties props,String key){ return getBoolean(props,key,false); } /** * 获取布尔型属性(可指定默认值) * @param props * @param key * @param defaultValue * @return */ public static boolean getBoolean(Properties props,String key,Boolean defaultValue){ boolean value = defaultValue; if (props.containsKey(key)){ value = CastUtil.castBoolean(props.getProperty(key)); } return value; } }

用到的maven坐标

        
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
            <version>1.7.9version>
        dependency>

常用流操作工具类

 StreamUtil.java

public class StreamUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(StreamUtil.class);

    /**
     * 从输入流中获取字符串
     * @param is
     * @return
     */
    public static String getString(InputStream is){
        StringBuilder sb = new StringBuilder();
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
            String line;
            while((line=reader.readLine())!=null){
                sb.append(line);
            }
        } catch (IOException e) {
            LOGGER.error("get string failure",e);
            throw new RuntimeException(e);
        }
        return sb.toString();
    }

}

编码工具类

public class CodecUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(CodecUtil.class);

    /**
     * 将URL编码
     */
    public static String encodeURL(String source){
        String target;
        try {
            target = URLEncoder.encode(source,"utf-8");
        } catch (UnsupportedEncodingException e) {
            LOGGER.error("encode url failure",e);
            throw new RuntimeException(e);
            //e.printStackTrace();
        }
        return target;
    }

    /**
     * 将URL解码
     */
    public static String dencodeURL(String source){
        String target;
        try {
            target = URLDecoder.decode(source,"utf-8");
        } catch (UnsupportedEncodingException e) {
            LOGGER.error("encode url failure",e);
            throw new RuntimeException(e);
            //e.printStackTrace();
        }
        return target;
    }
}

Json工具类

package org.smart4j.framework.util;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

/**
 * @program: JsonUtil
 * @description: JSON工具类
 * @author: Created by QiuYu
 * @create: 2018-10-24 15:55
 */

public class JsonUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(JsonUtil.class);

    private static final ObjectMapper OBJECT_MAPPER =new ObjectMapper();

    /**
     * 将POJO转换为JSON
     */
    public static  String toJson(T obj){
        String json;
        try {
            json = OBJECT_MAPPER.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            LOGGER.error("convert POJO to JSON failure",e);
            throw new RuntimeException(e);
            //e.printStackTrace();
        }
        return json;
    }

    /**
     * 将JSON转为POJO
     */
    public static  T fromJson(String json,Class type){
        T pojo;
        try {
            pojo = OBJECT_MAPPER.readValue(json,type);
        } catch (IOException e) {
            LOGGER.error("convert JSON to POJO failure",e);
            throw new RuntimeException(e);
            //e.printStackTrace();
        }
        return pojo;

    }
}

日期工具类

DataUtil.java

     /**
      * 根据年月获取当月最后一天
      * @param yearmonth yyyy-MM
      * @return yyyy-MM-dd
      * @throws ParseException
      */
     public static String getLastDayOfMonth(String yearmonth) {
         try {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM");
             Date dd = format.parse(yearmonth);
             Calendar cal = Calendar.getInstance();
             cal.setTime(dd);
             int cc=cal.getActualMaximum(Calendar.DAY_OF_MONTH);
             String result = yearmonth+"-"+cc;
             return result;
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return null;
     }

下载文件工具类

    /**
     * 下载url的文件到指定文件路径里面,如果文件父文件夹不存在则自动创建
     * url 下载的http地址
     * path 文件存储地址
     * return 如果文件大小大于2k则返回true
     */
    public static boolean downloadCreateDir(String url,String path){
        HttpURLConnection connection=null;
        InputStream in = null;
        FileOutputStream o=null;
        try{
            URL httpUrl=new URL(url);
            connection = (HttpURLConnection) httpUrl.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("Charset", "gbk");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            connection.setRequestMethod("GET");
            
            byte[] data=new byte[1024];
            File f=new File(path);
            File parentDir = f.getParentFile();
            if (!parentDir.exists()) {
                parentDir.mkdirs();
            }
            if(connection.getResponseCode() == 200){
                in = connection.getInputStream();
                o=new FileOutputStream(path);
                int n=0;
                while((n=in.read(data))>0){
                    o.write(data, 0, n);
                    o.flush();
                }
            }
            if(f.length()>2048){  //代表文件大小
                return true;  //如果文件大于2k则返回true
            }
        }catch(Exception ex){
            ex.printStackTrace();
        }finally{
            try{
                if(in != null){
                    in.close();
                }
            }catch(IOException ex){
                ex.printStackTrace();
            }
            try{o.close();}catch(Exception ex){}
            try{connection.disconnect();}catch(Exception ex){}
        }
        return false;
    }

解压ZIP工具类

package com.***.tools;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/**
 * 解压zip文件
 */
public final class ZipUtil {
    private static final int buffer = 2048;

    /**
     * 解压Zip文件
     * @param path zip文件目录
     */
    public static void unZip(String path) {
        int count = -1;
        String savepath = "";

        File file = null;
        InputStream is = null;
        FileOutputStream fos = null;
        BufferedOutputStream bos = null;

        savepath = path.substring(0, path.lastIndexOf(".")) + File.separator; // 保存解压文件目录
        new File(savepath).mkdir(); // 创建保存目录
        ZipFile zipFile = null;
        try {
            zipFile = new ZipFile(path,Charset.forName("GBK")); // 解决中文乱码问题
            Enumeration entries = zipFile.entries();  //枚举ZIP中的所有文件

            while (entries.hasMoreElements()) {
                byte buf[] = new byte[buffer];

                ZipEntry entry = (ZipEntry) entries.nextElement();

                String filename = entry.getName();  //获取文件名
                filename = savepath + filename;
                boolean ismkdir = false;
                if (filename.lastIndexOf("/") != -1) { // 检查此文件是否带有文件夹
                    ismkdir = true;
                }

                if (entry.isDirectory()) { // 如果此枚举文件是文件夹则创建,并且遍历下一个
                    file = new File(filename);
                    file.mkdirs();
                    continue;
                }
                file = new File(filename);  //此枚举文件不是目录
                if (!file.exists()) {  //如果文件不存在并且文件带有目录
                    if (ismkdir) {
                        new File(filename.substring(0, filename
                                .lastIndexOf("/"))).mkdirs(); // 先创建目录
                    }
                }
                file.createNewFile(); //再创建文件

                is = zipFile.getInputStream(entry);
                fos = new FileOutputStream(file);
                bos = new BufferedOutputStream(fos, buffer);

                while ((count = is.read(buf)) > -1) {
                    bos.write(buf, 0, count);
                }
                bos.flush();
            }
        } catch (IOException ioe) {
            ioe.printStackTrace();
        } finally {
            try {
                if (bos != null) {
                    bos.close();
                }
                if (fos != null) {
                    fos.close();
                }
                if (is != null) {
                    is.close();
                }
                if (zipFile != null) {
                    zipFile.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

文件编码转码

将GBK编码的文件转为UTF-8编码的文件

经常配合上一个使用,下载的压缩包解压为文件然后解码。

    /**
     * 把GBK文件转为UTF-8
     * 两个参数值可以为同一个路径
     * @param srcFileName 源文件
     * @param destFileName 目标文件
     * @throws IOException
     */
    private static void transferFile(String srcFileName, String destFileName) throws IOException {
        String line_separator = System.getProperty("line.separator"); 
        FileInputStream fis = new FileInputStream(srcFileName);
        StringBuffer content = new StringBuffer();
        DataInputStream in = new DataInputStream(fis);
        BufferedReader d = new BufferedReader(new InputStreamReader(in, "GBK"));  //源文件的编码方式
        String line = null;
        while ((line = d.readLine()) != null)
         content.append(line + line_separator);
        d.close();
        in.close();
        fis.close();
            
        Writer ow = new OutputStreamWriter(new FileOutputStream(destFileName), "utf-8");  //需要转换的编码方式
        ow.write(content.toString());
        ow.close();
    }

 

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