System.out：标准输出设备（默认是：控制台）
System.in：标准输入设备（默认是：键盘）
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InputStream in = System.in;
int by = in.read();
sysout(by);
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InputStream in = System.in;
StringBuilder sb = new StringBuilder();
while(true){
int ch = in.read();
if(ch==’\r’){
continue;
}
if(ch==’\n’){
String s = sb.toString();
if(“over”.equals(s)){
break;
}
System.out.prinltn(s.toUpperCase());
sb.delete(0, sb.length());
}
else
sb.append((char)ch);
}