Java 常用工具方法

1、IO相关 1.1、InputStream转换为字符串

• 方法一：

public String inputStream2String(InputStream is) throws Exception{  //字节流转为字符流
    BufferedReader reader = new BufferedReader(new InputStreamReader(is,"UTF-8"));  
    StringBuffer buffer = new StringBuffer();
    String line = "";
    while ((line = reader.readLine()) != null) {
	    buffer.append(line);
    }
    reader.close();
    return buffer.toString();
}

• 方法二：

public static String inputStream2String(InputStream is) {
	String res = new BufferedReader(new InputStreamReader(is))
			.lines()
			.collect(Collectors.joining("\n"));
	return res;
}

• 方法三：

public static String inputStream2String(InputStream is) {
	String res = new BufferedReader(new InputStreamReader(is))
			.lines()
			.parallel()
			.collect(Collectors.joining("\n"));
	return res;
}

• 方法四：

public	String inputStream2String(InputStream is) throws Exception {
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	byte[] buffer = new byte[512];// 读取缓存
	int length = 0;
	while ((length = is.read(buffer)) != -1) {
		baos.write(buffer, 0, length);// 写入输出流
	}
	baos.close();// 读取完毕，关闭输入流
	return new String(baos.toByteArray(), "UTF-8");// 根据输出流创建字符串对象
}

• 方法五：

public static String inputStream2String(InputStream is) throws IOException {
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	byte[] buffer = new byte[512];// 读取缓存
	int length = 0;
	while ((length = is.read(buffer)) != -1) {
		baos.write(buffer, 0, length);// 写入输出流
	}
	baos.close();// 读取完毕，关闭输入流
	return  baos.toString("UTF-8");
}

• 方法六：

public static String inputStream2String(InputStream is) {
	Scanner scanner = new Scanner(is).useDelimiter("\\A");
	String res  = scanner.hasNext()?scanner.next():"";
	return res;
}

• 方法七：

public static String inputStream2String(InputStream is) throws IOException {
	BufferedInputStream bis = new BufferedInputStream(is);
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	int res = bis.read();
	while(res != -1) {
		baos.write((byte)res);
		res = bis.read();
	}
	return  baos.toString("UTF-8");
}

• 方法八（汉字乱码）：

public static String inputStream2String(InputStream is) throws IOException {
	int ch;
	StringBuilder sb = new StringBuilder();
	while((ch = is.read()) != -1) {
		sb.append((char)ch);
	}

	return  sb.toString();
}

1.2、字符串转换为InputStream

public InputStream string2InputStream(String str) {
    ByteArrayInputStream stream = new ByteArrayInputStream(str.getBytes());
    return stream;
}

2、日期相关 2.1、获取指定时间所对应的timestamp

public long getTimestamp(String date){
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    long res = 0;
    try {
        res = sdf.parse(date).getTime() / 1000;
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return  res;
}

2.2、java.util.Date与java.sql.Date之间相互转换

public void date2Date() {
    java.util.Date uDate = new java.util.Date();
    java.sql.Date sDate = new java.sql.Date(uDate.getTime());
    uDate = sDate;
}

3、图片与字节数组 3.1、图片转字节数组

public byte[] img2byteArray(String path) {
    try (FileImageInputStream input = new FileImageInputStream(new File(path));
         ByteArrayOutputStream output = new ByteArrayOutputStream();) {
        byte[] buf = new byte[1024];
        int numBytesRead = 0;
        while ((numBytesRead = input.read(buf)) != -1) {
            output.write(buf, 0, numBytesRead);
        }
        return output.toByteArray();
    } catch (IOException ex1) {
        ex1.printStackTrace();
    }
    return null;
}

3.2、字节数组转图片

/**
 * 字节数组转换为图片
 *
 * @param data 待转换的字节数组
 * @param path 生成的图片的名称（带路径）
 */
public void byteArray2img(byte[] data, String path) {
    if (data.length