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This noncompliant code example casts the value returned by the read() method directly to a value of type byte and then compares this value with -1 in an attempt to detect the end of the stream. This conversion leaves the value of c as 0xFFFF (e.g., Character.MAX_VALUE) instead of -1. Consequently, the test for the end of stream never evaluates to true (because the char type is unsigned and the value of c is 0-extended to 0x0000FFFF).

FileInputStream in;
// initialize stream 
byte data;
while ((data = (byte) in.read()) != -1) { 
  // ... 
}

When If the return value of read() method is cast to the byte value 0xFF, the returned byte encounters a 0xFF byte in the file, this value is indistinguishable from the -1 value used to indicate the end of stream, because the byte value is promoted and sign-extended to an int before being compared with -1. Consequently, the loop can halt prematurely if a 0xFF byte is read.

Compliant Solution (byte)

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This noncompliant code example casts the value of type int returned by the read() method directly to a value of type char, which is then compared with -1 in an attempt to detect the end of stream. This conversion leaves the value of c data as 0xFFFF (e.g., Character.MAX_VALUE) instead of -1. Consequently, the test for the end of stream file never evaluates to true.

FileReader in;
// initialize stream 
char cdata;
while ((cdata = (char) in.read()) != -1) { 
  // ... 
}

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