Break long getTime() into 4 shorts not really work Modbus

Question

I am a beginner and I want to divide a long gettime into 4 shorts for the Modbus protocol, but it does not always work. I don't know why (maybe because of the casting). I hope someone may help me :)

Thanks in advance to those who can enlighten me!

public void SetUp() {
    long time = new Date().getTime();  // time in ms since epoch
    System.out.println(time);
    int high32 = (int)(time >> 32);
    int low32 = (int)time;
    long l = (((long)high32) << 32) | (low32 & 0xffffffffL);
    short low16_1 = (short) high32;
    short high16_1= (short) (high32 >> 16);
    int complete = low16_1 | (high16_1 << 16);
    short low16_2 = (short) low32;
    short high16_2= (short) (low32 >> 16);
    int complete2 = low16_2 | (high16_2 << 16);
    long d = (((long)complete) << 32) | (complete2 & 0xffffffffL);
    System.out.println(l);      
    System.out.println(d);
    Date e = new Date (time);
    System.out.println(e);
    Date g = new Date (d);
    System.out.println(g);
}

Display example :

1530430114623
1530430114623
1530430114623
Sun Jul 01 09:28:34 CEST 2018
Sun Jul 01 09:28:34 CEST 2018

1530431375214
1530431375214
1533303293806
Sun Jul 01 09:49:35 CEST 2018
Fri Aug 03 15:34:53 CEST 2018

Answer 1

Just use a union

This is how to convert from 1 long(32 bits) to 4 uint8 (8bit)

union convertor{
long input;
uint8_t output[4];
}

convertor entry;
entry.input=new Date().getTime()
//the value will be split into 4 unit8_t of entry.output

You can do something similar with unit16_t, here you will have to use 2 unit16_t instead of 4.

You can then combine the shorts together in the same ourder where it is being received to get the original time value

for(int i=0;i<4;i++)
entry.output[i]=data[i];
//get the original value from entry.intput as long