想请问一下while语句中的！=-1是什么意思呢

Question

public static void main(String[] args) {
//声明两个文件读入流
FileInputStream in1 = null,in2 = null;
//声明一个序列流
SequenceInputStream s = null;
//声明一个输出流
FileOutputStream out = null;
try {
//构造两个被读入的文件
File inputFile1 = new File("d:\\1.txt");
File inputFile2 = new File("d:\\2.txt");
//构造一个输出文件
File outputFile = new File("d:\\1and2.txt");

in1 = new FileInputStream(inputFile1);
in2 = new FileInputStream(inputFile2);

//将两个输入流合为一个输入流
s = new SequenceInputStream(in1,in2);
out = new FileOutputStream(outputFile);

int c;
while((c = s.read())!=-1) {
out.write(c);
}
in1.close();
in2.close();
s.close();
System.out.println("ok....");
}catch(IOException e) {
e.printStackTrace();
}
}

Answer 1

行从0开始，不等-1说明有读到行。