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Thread: Learning Java

  1. #1
    dn54321 is offline Member
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    Default Learning Java

    Hey Guys, I just recently started coding java and i have a problem.... So I was doing an exercise on LearnJavaOnline. The exercise was: Create all the the primitives with different values. Concatenate them into a string and print it to the screen so it will print: H3110 w0r1d 2.0 true

    I attempted it and this is what i wrote

    public static void main(String[] args) {
    char H = 'h';
    byte e = 3;
    short l = 1;
    int L = 1;
    long o = 0;

    char w = 'w';
    float O = 0;
    char r = 'r';
    int one = 1;
    char d = 'd';

    double two = 2.0;
    boolean hi = true;
    String HelloWorld = H+e+l+L+o+" "+w+0+r+one+d+" "+two+" "+hi;

    However it prints "109 w0r1d 2.0 true"
    But when i add 2 speech marks: String HelloWorld = H+""+e+l+L+o+" "+w+0+r+one+d+" "+two+" "+hi;
    It works perfectly, why is that? i'm dumb :C

  2. #2
    Norm's Avatar
    Norm is online now Moderator
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    Jun 2008
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    Default Re: Learning Java

    The + operator is used two ways:
    math sum: 1+2 = 3
    String concatenation.: "1" + "2" = "12"

    The compiler looks at the operands on either side of the + to decide which operation to do.
    If the two operands can converted to an int, then they are summed.
    If there is a String, then the operands are concatenated.
    If you don't understand my response, don't ignore it, ask a question.

  3. #3
    coolman50544 is offline Member
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    Apr 2014
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    Default Re: Learning Java

    Don't forget their are other methods like the append() method for the string class. You can also use a StringBuilder object if you'd like. For more information just look at the API or some tutorials. Happy Coding

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