ConvertUtils.java

package com.jingewenku.abrahamcaijin.commonutil;

/**
 * @Description:主要功能: 类型转换类
 * @Prject: CommonUtilLibrary
 * @Package: com.jingewenku.abrahamcaijin.commonutil
 * @author: AbrahamCaiJin
 * @date: 2017年05月16日 15:26
 * @Copyright: 个人版权所有
 * @Company:
 * @version: 1.0.0
 */

public class ConvertUtils {

    private ConvertUtils() {
        throw new UnsupportedOperationException("cannot be instantiated");
    }

    /**
     * 十六进制字符串转换为byte数组
     *
     * @param hexString
     * @return
     */
    public static byte[] hexStringToBytes(String hexString) {
        if (hexString == null || hexString.equals("")) {
            return null;
        }
        hexString = hexString.toUpperCase();
        int length = hexString.length() / 2;
        char[] hexChars = hexString.toCharArray();
        byte[] d = new byte[length];
        for (int i = 0; i < length; i++) {
            int pos = i * 2;
            d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
        }
        return d;
    }

    /**
     * char转换为byte数组
     * @param c
     * @return
     */
    public static byte charToByte(char c) {
        return (byte) "0123456789ABCDEF".indexOf(c);
    }


    /**
     * byte数组转换为十六进制字符串
     *
     * @param b
     * @return
     */
    public static String bytesToHexString(byte[] b) {
        if (b.length == 0) {
            return null;
        }
        StringBuilder sb = new StringBuilder("");
        for (int i = 0; i < b.length; i++) {
            int value = b[i] & 0xFF;
            String hv = Integer.toHexString(value);
            if (hv.length() < 2) {
                sb.append(0);
            }

            sb.append(hv);
        }
        return sb.toString();
    }

    /**
     * int转换为byte数组
     *
     * @param res
     * @return
     */
    public static byte[] intToByte(int res) {
        byte[] targets = new byte[4];
        targets[0] = (byte) (res & 0xff);// 最低位
        targets[1] = (byte) ((res >> 8) & 0xff);// 次低位
        targets[2] = (byte) ((res >> 16) & 0xff);// 次高位
        targets[3] = (byte) (res >>> 24);// 最高位,无符号右移。
        return targets;
    }

    /**
     * byte数组转换为int
     *
     * @param res
     * @return
     */
    public static int byteToInt(byte[] res) {
        // 一个byte数据左移24位变成0x??000000，再右移8位变成0x00??0000
        int targets = (res[3] & 0xff) | ((res[2] << 8) & 0xff00) | ((res[1] << 16) & 0xff0000) | ((res[0] << 24) & 0xff000000);
        return targets;
    }

    /**
     * 保留几位小数
     */
    public static String saveDecimals(int cnt, double value) {
        if (cnt == 2)
            return String.format("%.02f", value);
        else if (cnt == 1)
            return String.format("%.01f", value);
        else
            return String.format("%.0f", value);
    }

}