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In particular, comparing a value of type {{char}} with -1 will never yield {{true}}. However, because the method {{read()}} returns -1 to indicate {{EOF}}, it is tempting to try to compare the character returned by {{read()}} with -1. This is a common error \[[Pugh 08|AA. Java References#Pugh 08]\]. |
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In this noncompliant code, the value of type int returned by the read() method is cast directly to a char, and that value of type char which is compared with -1 to try to detect EOF. This conversion leaves the value of c as 0xffff (Character.MAX_VALUE) instead of -1. Hence, this test never evaluates to true.
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Always use a signed type of sufficient size to store signed data. To be compliant, use an a value of type int type to check for EOF while reading in data. If the value of type int value returned by read() is not -1, then it can be safely cast to a value of type char.
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int c;
while ((c=in.read())!= -1) {ch = (char)c; ... }
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