How to efficiently convert byte array to string

Question

I have a byte array of 151 bytes which is typically a record, The record needs to inserted in to a oracle database. In 151 byte of array range from 0 to 1 is a record id , 2 to 3 is an reference id , 4 to 9 is a date value. The following data in an byte array is a date value. i want to convert it to string

byte[] b= {48,48,49,48,48,52};  // when converted to string it becomes 10042. 

new String(b);  // current approach

is there any way to efficiently to convert byte array of some range (Arrays.copyOfRange(b,0,5)) to string .

@Martjin i have file which has 527890 bytes and i have to read the chunk of 2048 bytes which has 13 records , each record is 151 bytes , and we have to extract the ranges and store in table columns.;) — Dead Programmer
– Dead Programmer, Commented Dec 29, 2010 at 13:38

user229044 · Accepted Answer · 2020-02-11 18:41:18Z

18

new String(b, 0 ,5);

See the API doc for more information.

edited Feb 11, 2020 at 18:41

user229044♦

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answered Dec 29, 2010 at 11:05

Michael Borgwardt

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1 Comment

Michael Borgwardt Over a year ago

@Rekin: no, Suresh specifially does NOT want to use the entire byte array. If he did, it would be much simpler: new String(b)

moinudin · Accepted Answer · 2010-12-29 11:04:28Z

1

Use the String(bytes[] bytes, int offset, int length) constructor: http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#String(byte[], int, int)

new String(b, 0, 5);

answered Dec 29, 2010 at 11:04

moinudin

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Comments

rodion · Accepted Answer · 2010-12-29 12:07:58Z

1

If you need to create a string for each region in the record, I would suggest a substring approach:

byte[] wholeRecord = {0,1,2 .. all record goes here .. 151}
String wholeString = new String(wholeRecord);
String id = wholeString.substring(0,1);
String refId = wholeString.substring(1,3);
...

The actual offsets may be different depending on string encoding.

The advantage of this approach is that the byte array is only copied once. Subsequent calls to substring() will not create copies, but will simply reference the first copy with offsets. So you can save some memory and array copying time.

answered Dec 29, 2010 at 12:07

rodion

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1 Comment

Dead Programmer Over a year ago

thanks. but u said offset would be different . how to do that dynamically depending upon offset.

Drew Noakes · Accepted Answer · 2017-09-07 20:10:10Z

1

None of the answers here consider that you might not be using ASCII. When converting bytes to a string, you should always consider the charset.

new String(bytes, offset, length, charset);

answered Sep 7, 2017 at 20:10

Drew Noakes

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1 Comment

Tom Blodget Over a year ago

This is the right answer. (But, even worse than ASCII, that other overload uses the default encoding, which varies from time to time, user to user, system to system.)

user467871 · Accepted Answer · 2010-12-29 11:11:52Z

-1

and here fantastic way (not efficient) :)

    byte[] b = { 48, 48, 49, 48, 48, 52 };
    ByteArrayInputStream bais = new ByteArrayInputStream(b);

    BufferedReader buf = new BufferedReader(new InputStreamReader(bais));

    String s = buf.readLine();
    System.out.println(s);

answered Dec 29, 2010 at 11:11

user467871

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