Conversions in Java

Discussion in 'Java' started by Panoramix, May 21, 2013.

  1. Panoramix

    Panoramix Guest

    Someone has a good introduction to conversions of values in Java?

    I am working in a project that I need to use this and I'm having some trouble about this.


    Thanks!
    Panoramix, May 21, 2013
    #1
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  2. Panoramix

    Arne Vajhøj Guest

    On 5/21/2013 11:23 AM, Panoramix wrote:
    > Someone has a good introduction to conversions of values in Java?
    >
    > I am working in a project that I need to use this and I'm having some trouble about this.


    What type of conversions?

    Arne
    Arne Vajhøj, May 21, 2013
    #2
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  3. Panoramix

    Stefan Ram Guest

    Panoramix <> writes:
    >Someone has a good introduction to conversions of values in Java?


    There are no special books about the conversions of values
    in Java, but the topic is treated in every good Java text book.

    >I am working in a project that I need to use this and I'm having some trouble about this.


    Possibly, you might want

    java.lang.Double.valueOf( yourText )
    Stefan Ram, May 21, 2013
    #3
  4. On 05/21/2013 12:34 PM, Stefan Ram wrote:
    > Panoramix <> writes:
    >> Someone has a good introduction to conversions of values in Java?

    >
    > There are no special books about the conversions of values
    > in Java, but the topic is treated in every good Java text book.


    And the language spec and type APIs.

    >> I am working in a project that I need to use this and I'm having some trouble about this.

    >
    > Possibly, you might want
    >
    > java.lang.Double.valueOf( yourText )
    >

    Good point, both Arne and Stefan - it may not be simply implicit numeric
    type conversions referred to here, but also parsing string into numeric,
    etc etc.

    AHS
    Arved Sandstrom, May 21, 2013
    #4
  5. Panoramix

    Lew Guest

    Stefan Ram wrote:
    > Panoramix writes:
    >> Someone has a good introduction to conversions of values in Java?


    Arne asked "What type of conversions?" Here is some general information about various
    conversion types:

    http://docs.oracle.com/javase/tutorial/java/data/converting.html
    http://docs.oracle.com/javase/tutorial/java/data/autoboxing.html
    http://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html
    http://docs.oracle.com/javase/tutorial/essential/io/scanfor.html
    http://docs.oracle.com/javase/tutorial/java/IandI/interfaceAsType.html

    If you read the Java Language Specification (JLS) you will get the normative definitions
    for various conversions:
    http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html

    If you mean various formatting or string conversions, as Stefan conjectured, then you
    should look at the Javadocs for various formatting and string-ish types:
    http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#format(java.lang.String, java.lang.Object...)
    et al.
    http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html
    http://docs.oracle.com/javase/7/docs/api/java/text/Format.html
    and related types

    > There are no special books about the conversions of values
    > in Java, but the topic is treated in every good Java text book.
    >
    >> I am working in a project that I need to use this and I'm having some trouble about this.

    >
    > Possibly, you might want
    >
    > java.lang.Double.valueOf( yourText )


    There are similar 'valueOf()' methods in the other primitive wrapper classes ('Integer', ...).

    Also, GIYF.

    --
    Lew
    Lew, May 21, 2013
    #5
  6. Panoramix

    Panoramix Guest

    Thanks guys!

    I really appreciate.

    When I say conversions, I mean every type of conversion!

    Thanks for the help
    Panoramix, May 21, 2013
    #6
  7. Panoramix

    Eric Sosman Guest

    On 5/21/2013 6:07 PM, Panoramix wrote:
    > Thanks guys!
    >
    > I really appreciate.
    >
    > When I say conversions, I mean every type of conversion!


    There's a reasonably accurate summary at

    <http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html>

    > Thanks for the help


    Glad to be of service.

    --
    Eric Sosman
    d
    Eric Sosman, May 21, 2013
    #7
  8. Panoramix

    Roedy Green Guest

    On Tue, 21 May 2013 08:23:13 -0700 (PDT), Panoramix
    <> wrote, quoted or indirectly quoted someone
    who said :

    >Someone has a good introduction to conversions of values in Java?


    see http://mindprod.com/applet/converter.html
    --
    Roedy Green Canadian Mind Products http://mindprod.com
    Technological possibilities are irresistible to man.
    If man can go to the moon, he will.
    If he can control the climate, he will.
    ~ John von Neumann (born: 1903-12-28 died: 1957-02-08 at age: 53)
    Roedy Green, May 22, 2013
    #8
  9. On 22.05.2013 00:07, Panoramix wrote:

    > When I say conversions, I mean every type of conversion!


    Well, then you just need

    public interface Converter<F,T> {
    T convert(F fromValue);
    }

    implement all conversions needed plus a smart mechanism to choose the
    appropriate one in every case. ;-)

    Cheers

    robert

    --
    remember.guy do |as, often| as.you_can - without end
    http://blog.rubybestpractices.com/
    Robert Klemme, May 25, 2013
    #9
  10. On 05/25/2013 06:27 PM, Robert Klemme wrote:
    > On 22.05.2013 00:07, Panoramix wrote:
    >
    >> When I say conversions, I mean every type of conversion!

    >
    > Well, then you just need
    >
    > public interface Converter<F,T> {
    > T convert(F fromValue);
    > }
    >
    > implement all conversions needed plus a smart mechanism to choose the
    > appropriate one in every case. ;-)
    >
    > Cheers
    >
    > robert
    >

    JSF javax.faces.convert.Converter. :) You've got to do the custom work
    and the mechanism is explicit, but still...

    A fair few ESBs (enterprise service buses) also have what they call
    transformers (converters) and often a registration/auto-discovery
    mechanism. For example, in Java-based ESBs - which is most of them - you
    might have a message which encounters a processing component, which by
    entry point resolution, expects a payload of class X and to return a
    payload of class Y (null is acceptable): the ESB will consult a list of
    X<->Y converters that it knows about, and select the best converter
    according to a rule set.

    AHS
    --
    When a true genius appears, you can know him by this sign:
    that all the dunces are in a confederacy against him.
    -- Jonathan Swift
    Arved Sandstrom, May 25, 2013
    #10
  11. Panoramix

    Arne Vajhøj Guest

    On 5/21/2013 6:07 PM, Panoramix wrote:
    > When I say conversions, I mean every type of conversion!


    Numbers of possible types are infinite.

    So number of conversions between types are also infinite.

    But if you are only thinking about the most basic types
    then see below for some examples.

    Arne

    ====

    int iv = 123;
    double xv2;
    xv2 = iv;

    int iv = 123;
    boolean bv2;
    bv2 = (iv != 0);

    int iv = 123;
    char cv2;
    cv2 = (char)iv;

    int iv = 123;
    String sv2;
    sv2 = Integer.toString(iv);

    double xv = 123.456;
    int iv2;
    iv2 = (int)xv;

    double xv = 123.456;
    String sv2;
    sv2 = Double.toString(xv);

    boolean bv = true;
    int iv2;
    iv2 = (bv ? 1 : 0);

    boolean bv = true;
    String sv2;
    sv2 = (new Boolean(bv)).toString();

    char cv = 'A';
    int iv2;
    iv2 = cv;

    char cv = 'A';
    String sv2;
    sv2 = new String(new char[] { cv });

    String sv = "123";
    int iv2;
    iv2 = Integer.parseInt(sv);

    String sv = "123.456";
    double xv2;
    xv2 = Double.parseDouble(sv);

    String sv = "true";
    boolean bv2;
    bv2 = Boolean.valueOf(sv).booleanValue();

    String sv = "ABC";
    char cv2;
    cv2 = sv.charAt(0);

    int iv = 123;
    String sv2;
    sv2 = Integer.toHexString(iv);

    String sv = "7b";
    int iv2;
    iv2 = Integer.parseInt(sv, 16);

    byte[] b = { 65, 66, 67 };
    String s2;
    s2 = new String(b, "ISO-8859-1");

    String s = "abc";
    byte[] b2;
    b2 = s.getBytes("ISO-8859-1");

    int iv = 123;
    Integer iv2;
    iv2 = new Integer(iv);

    Integer iv = new Integer(123);
    int iv2;
    iv2 = iv.intValue();

    java.util.Date d;
    java.util.Calendar cal = new java.util.GregorianCalendar();
    d = cal.getTime();

    java.util.Date d = new java.util.Date();
    java.util.Calendar cal = new java.util.GregorianCalendar();
    cal.setTime(d);

    java.util.Date d = new java.util.Date();
    java.text.DateFormat df = new
    java.text.SimpleDateFormat("dd-MMM-yyyy hh:mm");
    String ds;
    ds = df.format(d);

    String ds = "31-Jan-2004 09:24"
    java.util.Date d;
    java.text.DateFormat df = new
    java.text.SimpleDateFormat("dd-MMM-yyyy hh:mm");
    d = df.parse(ds);

    java.util.Date d = new java.util.Date();
    java.sql.Timestamp ts;
    ts = new java.sql.Timestamp(d.getTime());

    java.sql.Timestamp ts = new java.sql.Timestamp((new Date()).getTime());
    java.util.Date d;
    d = ts;
    Arne Vajhøj, Jun 2, 2013
    #11
  12. Don't forget shorthand operators that automatically typecast:

    +=
    -=
    *=
    /=

    int a= 0;
    a+= Double.MAX_VALUE;
    a+= Float.MAX_VALUE;
    a+= Long.MAX_VALUE;

    The shorthand bit operators automatically typecast length:

    |=
    &=
    ^=

    a|= Long.MAX_VALUE;



    In article <51aaa795$0$32106$>,
    Arne Vajhøj <> wrote:

    > On 5/21/2013 6:07 PM, Panoramix wrote:
    > > When I say conversions, I mean every type of conversion!

    >
    > Numbers of possible types are infinite.
    >
    > So number of conversions between types are also infinite.
    >
    > But if you are only thinking about the most basic types
    > then see below for some examples.
    >
    > Arne
    >
    > ====
    >
    > int iv = 123;
    > double xv2;
    > xv2 = iv;
    >
    > int iv = 123;
    > boolean bv2;
    > bv2 = (iv != 0);
    >
    > int iv = 123;
    > char cv2;
    > cv2 = (char)iv;
    >
    > int iv = 123;
    > String sv2;
    > sv2 = Integer.toString(iv);
    >
    > double xv = 123.456;
    > int iv2;
    > iv2 = (int)xv;
    >
    > double xv = 123.456;
    > String sv2;
    > sv2 = Double.toString(xv);
    >
    > boolean bv = true;
    > int iv2;
    > iv2 = (bv ? 1 : 0);
    >
    > boolean bv = true;
    > String sv2;
    > sv2 = (new Boolean(bv)).toString();
    >
    > char cv = 'A';
    > int iv2;
    > iv2 = cv;
    >
    > char cv = 'A';
    > String sv2;
    > sv2 = new String(new char[] { cv });
    >
    > String sv = "123";
    > int iv2;
    > iv2 = Integer.parseInt(sv);
    >
    > String sv = "123.456";
    > double xv2;
    > xv2 = Double.parseDouble(sv);
    >
    > String sv = "true";
    > boolean bv2;
    > bv2 = Boolean.valueOf(sv).booleanValue();
    >
    > String sv = "ABC";
    > char cv2;
    > cv2 = sv.charAt(0);
    >
    > int iv = 123;
    > String sv2;
    > sv2 = Integer.toHexString(iv);
    >
    > String sv = "7b";
    > int iv2;
    > iv2 = Integer.parseInt(sv, 16);
    >
    > byte[] b = { 65, 66, 67 };
    > String s2;
    > s2 = new String(b, "ISO-8859-1");
    >
    > String s = "abc";
    > byte[] b2;
    > b2 = s.getBytes("ISO-8859-1");
    >
    > int iv = 123;
    > Integer iv2;
    > iv2 = new Integer(iv);
    >
    > Integer iv = new Integer(123);
    > int iv2;
    > iv2 = iv.intValue();
    >
    > java.util.Date d;
    > java.util.Calendar cal = new java.util.GregorianCalendar();
    > d = cal.getTime();
    >
    > java.util.Date d = new java.util.Date();
    > java.util.Calendar cal = new java.util.GregorianCalendar();
    > cal.setTime(d);
    >
    > java.util.Date d = new java.util.Date();
    > java.text.DateFormat df = new
    > java.text.SimpleDateFormat("dd-MMM-yyyy hh:mm");
    > String ds;
    > ds = df.format(d);
    >
    > String ds = "31-Jan-2004 09:24"
    > java.util.Date d;
    > java.text.DateFormat df = new
    > java.text.SimpleDateFormat("dd-MMM-yyyy hh:mm");
    > d = df.parse(ds);
    >
    > java.util.Date d = new java.util.Date();
    > java.sql.Timestamp ts;
    > ts = new java.sql.Timestamp(d.getTime());
    >
    > java.sql.Timestamp ts = new java.sql.Timestamp((new Date()).getTime());
    > java.util.Date d;
    > d = ts;

    --
    I will not see posts from Google because I must filter them as spam
    Kevin McMurtrie, Jun 2, 2013
    #12
  13. Panoramix

    Sven Köhler Guest

    On 06/02/2013 05:01 AM, Arne Vajhøj wrote:
    > On 5/21/2013 6:07 PM, Panoramix wrote:
    >> When I say conversions, I mean every type of conversion!

    >
    > Numbers of possible types are infinite.
    >
    > So number of conversions between types are also infinite.


    But the formal description of all possible conversions between types is
    not infinite.


    Regards,
    Sven
    Sven Köhler, Jun 2, 2013
    #13
  14. Panoramix

    Arne Vajhøj Guest

    On 6/2/2013 9:14 AM, Sven Köhler wrote:
    > On 06/02/2013 05:01 AM, Arne Vajhøj wrote:
    >> On 5/21/2013 6:07 PM, Panoramix wrote:
    >>> When I say conversions, I mean every type of conversion!

    >>
    >> Numbers of possible types are infinite.
    >>
    >> So number of conversions between types are also infinite.

    >
    > But the formal description of all possible conversions between types is
    > not infinite.


    True.

    But if someone want to ask that question and can understand the answer,
    then usually they don't need to ask in the first place.

    Arne
    Arne Vajhøj, Jun 2, 2013
    #14
  15. Panoramix

    Lew Guest

    Kevin McMurtrie wrote:
    > Don't forget shorthand operators that automatically typecast:


    The JLS doesn't call these "typecasts", it calls them "widening
    and narrowing conversions", in case you're looking for the rules
    at the source.

    > +=
    > -=
    > *=
    > /=
    >
    > int a= 0;
    > a+= Double.MAX_VALUE;
    > a+= Float.MAX_VALUE;
    > a+= Long.MAX_VALUE;
    >
    > The shorthand bit operators automatically typecast length:


    This is the same conversion as with += and the rest.

    > |=
    > &=
    > ^=
    >
    > a|= Long.MAX_VALUE;
    >
    > In article <51aaa795$0$32106$>,


    And please do not top-post.

    > Arne Vajhøj <> wrote:
    >> Panoramix wrote:


    --
    Lew
    Lew, Jun 2, 2013
    #15
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