关于tomcat下的编码问题

下面的代码是copy尚学堂张志宇老师的讲课资料，个人觉得比较经典就贴出来了。

public class TestB {
static String zhongwen = "中文";
static byte[] bytes = null;

public static void main(String[] args) throws Exception {
// GBK
//main1();
// utf-8
//main2();
// GBK-->utf-8-->GBK
//main3();
// GBK-->iso8859-1-->utf-8-->iso8859-1-->GBK
main4();

}
// GBK
public static void main1() throws Exception {
bytes = zhongwen.getBytes("GBK");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}
System.out.println(new String(bytes, "GBK"));
}
// utf-8
public static void main2() throws Exception {
bytes = zhongwen.getBytes("utf-8");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}
System.out.println(new String(bytes, "utf-8"));
}
// GBK-->utf-8-->GBK
public static void main3() throws Exception {

bytes = zhongwen.getBytes("GBK");
System.out.println("--------GBK----------");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}

bytes = zhongwen.getBytes("utf-8");
byte [] bytes_copy = bytes;
System.out.println("-------utf-8--------");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}

//错误的组装方法
System.out.println("-------error GBK--------");
zhongwen = new String(bytes, "GBK");
System.out.println(zhongwen);
bytes = zhongwen.getBytes("GBK");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}
//正确的组装方法
System.out.println("-------GBK--------");
System.out.println(new String(bytes_copy, "utf-8"));
}
// GBK-->iso8859-1-->utf-8-->iso8859-1-->GBK
public static void main4() throws Exception {

//最开始是GBK
bytes = zhongwen.getBytes("GBK");
System.out.println("--------GBK----------");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}

//被组装成了iso8859-1,new出的字符串对象有问题,但是字节内容没变
System.out.println("-------iso8859-1--------");
zhongwen = new String(zhongwen.getBytes("GBK"), "iso8859-1");
System.out.println(zhongwen);
bytes = zhongwen.getBytes("iso8859-1");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}
//转换成utf-8在网络上传输,一个byte转换为两个字节,所以一共8个字节
bytes = zhongwen.getBytes("utf-8");
System.out.println("-------utf-8--------");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}

//server端接收到utf-8,首先组装成iso8859-1,new出的字符串对象有问题,显示4个问号
System.out.println("-------server--iso8859-1------");
zhongwen = new String(bytes, "utf-8");
System.out.println(zhongwen);
bytes = zhongwen.getBytes("iso8859-1");
for (int i = 0; i < bytes.length; i++) {
System.out.println(Integer.toHexString(bytes[i]));
}

//以iso8859-1得到字节,并组装成GBK
System.out.println("-------GBK--------");
System.out.println(new String(bytes, "GBK"));
}



public static void ____________________main() throws Exception {
System.out.println(System.getProperty("file.encoding"));
System.out.println(System.getProperty("user.language"));
System.out.println(System.getProperty("user.region"));
}

}