Findbugs告诉我，我的非负值与-1的比较没有明显的原因

Question

我有这个代码在FindBugs中显示以下错误：

Bug: Bad comparison of nonnegative value with -1 in hydra.extensions.drivers.eg2.internal.EG2GatewaySimulator$1.run()

This code compares a value that is guaranteed to be non-negative with a negative constant or zero. 

Rank: Scary (5), confidence: High
Pattern: INT_BAD_COMPARISON_WITH_NONNEGATIVE_VALUE 
Type: INT, Category: CORRECTNESS (Correctness)

代码：

String receivedMessage = "";
char c;
boolean isValidChar;
do {
    c = (char) in.read();
    isValidChar = (c != '\r') && (c != -1);
    if (isValidChar) {
        receivedMessage += c;
    }
} while (isValidChar);

Answer 1

char值为16位非负值：

char：char数据类型是一个16位Unicode字符。它的最小值为'\ u0000'（或0），最大值为'\ uffff'（或65,535（含））。

您正在将它与-1进行比较。