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How many bytes does a string occupy in java?

王林

Release： 2019-11-22 15:39:33

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How many bytes does a string occupy in java?

First of all, char is the basic type of Java. The number of bytes occupied by the basic type is fixed. For example, int occupies 4 bytes and double occupies 8 bytes. This can make Java The types occupied on different platforms are fixed, which ensures the portability of Java. Therefore, the char type in Java fixedly occupies 2 bytes. (Note: The char type can also store a Chinese character).

Secondly, String is stored in a more flexible way. In String, one English character occupies 1 byte, while Chinese characters occupy different numbers of bytes depending on the encoding. Under UTF-8 encoding, one Chinese character occupies 3 bytes; while using GBK encoding, one Chinese character occupies 2 bytes.

The test code is as follows:

import java.io.UnsupportedEncodingException;

public class StrTest {

    public static void main(String[] args) throws UnsupportedEncodingException {
        String str1 = "hello";
        String str2 = "你好abc";

        System.out.println("utf-8编码下&#39;hello&#39;所占的字节数:" + str1.getBytes("utf-8").length);
        System.out.println("gbk编码下&#39;hello&#39;所占的字节数:" + str1.getBytes("gbk").length);

        System.out.println("utf-8编码下&#39;你好abc&#39;所占的字节数:" + str2.getBytes("utf-8").length);
        System.out.println("gbk编码下你好&#39;你好abc&#39;所占的字节数:" + str2.getBytes("gbk").length);
    }

}

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Output result:

utf-8编码下’hello’所占的字节数: 5
gbk编码下’hello’所占的字节数: 5
utf-8编码下’你好abc’所占的字节数: 9
gbk编码下你好’你好abc’所占的字节数: 7

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It can be seen that for String, one English character occupies 1 byte. Chinese characters occupy 2 (GBK encoding) or 3 (UTF-8 encoding) bytes. You can also use this method to check the status of other encodings, which will not be described here.

Finally, based on the characteristics of String, you can determine whether a string contains Chinese characters. The example is as follows:

public class StrTest {

    public static void main(String[] args) throws UnsupportedEncodingException {
        searchChineseCharacter("Good morning");
        searchChineseCharacter("hello 早上好");
    }

    //找出一个字符串中的汉字
    public static void searchChineseCharacter(String str){
        //正则表达式，用于匹配中文字符
        String regex = "[\u4e00-\u9fa5]";

        //如果str的长度和其所占字节数不等，说明包含中文
        if (str.length() != str.getBytes().length){
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(str);
            System.out.print("&#39;" + str + "&#39; 中的汉字为:");

            while (matcher.find()){
                System.out.print(matcher.group());
            }
        }

        else {
            System.out.println("&#39;" + str + "&#39; 中无汉字");
        }
    }

}

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Output result:

‘Good morning’ 中无汉字
‘hello 早上好’ 中的汉字为:早上好

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Recommended tutorial: java Getting Started Tutorial

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