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POArrayIndexOutOfBoundsException message
 

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  1. POArrayIndexOutOfBoundsException message
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    <p>I'm trying to write a program with a static method that accepts a single boolean array as its only parameter and then prints out the location of the first true, the last true, and the total number of trues in a string of consecutive true values. </p> <p>The program compiles fine. However, when I run it, only the first test is printed correctly. For the second test, I get an ArrayIndexOutOfBoundsException message. </p> <p>I've already read as many posts about it as I could find, but still haven't been able to make my program work properly. Any ideas as to what I'm doing wrong? Thanks so much!</p> <pre><code>class Bool { public static void main (String [] args) { boolean [] test1 = {false, true, true, true}; boolean [] test2 = {true}; boolean [] test3 = {true, true, true, true, false}; System.out.println ("For test 1: "); fullOfBool (test1); System.out.println ("For test 2: "); fullOfBool (test2); System.out.println ("For test 3: "); fullOfBool (test3); } public static void fullOfBool (boolean [] a) { int count = 0; int first = 0; int last = 0; for (int i = 0; i &lt;= a.length - 1; i++) { //this only finds the first true value in the array; either the value before was false or it's //already the first value in the array if (a[i] == true &amp;&amp; (a[i-1] != true || (i-1) &lt; 0) ) { first = i; System.out.println ("The first true occurs at position " + first + "."); break; //we can break because we've found the first true already } } for (int j = first; j &lt;= a.length - 1; j++) { if (a[j] == true) { count++; //(j+1) determines the last value; either (j+1) is false, in which case the a[j] is the last true, or //it is beyond the array's length, in which case a[j] is still the last true if ((((j+1) &lt; a.length) &amp;&amp; (a[j+1] != true)) || a.length == 1) { last = j; System.out.println ("The last true occurs at position " + j + "."); } } } System.out.println ("There was a sequence of " + count + " consecutive trues.\n"); } } </code></pre> <p>Thanks for all the input. You all were totally right, I overdid the first for-loop. Now I'm stuck on the second for-loop for j. It doesn't print anything for the first or second tests. I'm sure I've overdone this one as well, but can't figure out what needs to be fixed. </p> <pre><code> public static void fullOfBool (boolean [] a) { int count = 0; int first = 0; int last = 0; for (int i = 0; i &lt;= a.length - 1; i++) { //this only finds the first true value in the array; either the value before was false or it's //already the first value in the array if (a[i]) { first = i; System.out.println ("The first true occurs at position " + first + "."); break; //we can break because we've found the first true already } } for (int j = first; j &lt;= a.length - 1; j++) { if (a[j]) { count++; //(j+1) determines the last value; either (j+1) is false, in which case the a[j] is the last true, or //it is beyond the array's length, in which case a[j] is still the last true if ((((j+1) &lt; a.length) &amp;&amp; (a[j+1] != true))) { last = j; System.out.println ("The last true occurs at position " + j + "."); } } } </code></pre>
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    1. CODo you mean fullOfBool runs correctly the first time? Because I can see you trying to access `a[-1]` on the first iteration of the loop.
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    2. CO@splrs But in the first test, the array starts with **false**, hence it is working for that case.
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    3. COFor future reference, posting the full exception message is helpful. In your case, the message tells you the bad index value already: `Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1`.
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