The byte size problem occupied by har[] and String types

In C language

1, char a[10] = {"China"}, this How many bytes does a occupy?

Answer: It takes up 10 bytes.

Analysis: The above code assigns value to a,

a[0]='C', a[1]='h', a[2]='i' , a[3]='n', a[4]='a', a[5]='\0', a[6]='\0', a[7]='\0', a [8]='\0', a[9]='\0'

So, it occupies 10 bytes.

2. If it only refers to "China"?

Answer: A total of 6 bytes. China occupies 5 bytes, ends with '\0', and occupies 1 byte.

In Java language

1. How many bytes does String s = "China"; occupy?

Answer: 5 bytes.

 System.out.println(Charset.defaultCharset());//获取ide默认编码类型
String s = new String("China".getBytes());
byte[] b = s.getBytes();
System.out.println("" + b.length);

The above code can output that the byte length occupied by "China" is 5

2. How many bytes does String s = "China"; occupy?

Answer: If it is Chinese characters, encoding needs to be considered.

(1) In GBK encoding (ide default), each Chinese character occupies 2 bytes, then China occupies 4 bytes.

(2) When UTF-8 is encoded, each Chinese character occupies 3 bytes, so China occupies 6 bytes.

3. Transcoding problem, when converting GBK to UTF-8, will the byte usage increase? What about the other way around?

//获取的是 UTF-8编码
System.out.println(Charset.defaultCharset());
String s;
try {
        s = new String("中国".getBytes(),"GBK");
        byte[] b = s.getBytes();
        System.out.println("" + b.length);
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
}

The above code is: UTF-8 to GBK encoding format, the s length changes from 6 bytes to 9 bytes.

s Content changes: China —> Juan浗

Because the current encoding is UTF-8, it becomes 3 characters after transcoding, occupying 9 bytes. However, the reverse situation is like this:

China (gbk) —> ?й? (utf-8)

s The length changes from 4 bytes to 4 bytes, Although the length has not changed, the text has. here ? Occupies 1 byte

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