java中各种数据类型占用字节数

1字节(Byte)=8bit

java的基本类型

类型	所占字节
byte	1
short	2
int	4
long	8
float	4
double	8
char	2

String中字母和汉字所占字符是不一样的，并且与编码有关

英文字母：A

字节数	编码
1	GB2312
1	GBK
1	GB18030
1	ISO-8859-1
1	UTF-8
4	UTF-16
2	UTF-16BE
2	UTF-16-LE

中文汉字：我

字节数	编码
1	GB2312
2	GBK
2	GB18030
1	ISO-8859-1
3	UTF-8
4	UTF-16
2	UTF-16BE
2	UTF-16-LE

附录：计算String字节数的代码

package com.dingrui.stringbytelength;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.dozer.loader.api.FieldDefinition;

public class StringByteLength {

	/*
	 * GB2312 GBK GB18030 ISO-8859-1 UTF-8 UTF-16 UTF-16BE UTF-16LE
	 */
	public static void main(String[] args) throws IOException {

		String s1 = "a";
		String s2 = "龘";

		System.out.println(s1 + "  GB2312  " + s1.getBytes("GB2312").length);
		System.out.println(s1 + "  GBK  " + s1.getBytes("GBK").length);
		System.out.println(s1 + "  GB18030  " + s1.getBytes("GB18030").length);
		System.out.println(s1 + "  ISO-8859-1  " + s1.getBytes("ISO-8859-1").length);
		System.out.println(s1 + "  UTF-8  " + s1.getBytes("UTF-8").length);
		System.out.println(s1 + "  UTF-16  " + s1.getBytes("UTF-16").length);
		System.out.println(s1 + "  UTF-16BE  " + s1.getBytes("UTF-16BE").length);
		System.out.println(s1 + "  UTF-16LE  " + s1.getBytes("UTF-16LE").length);
		System.out.println("---------------");
		System.out.println(s2 + "  GB2312  " + s2.getBytes("GB2312").length);
		System.out.println(s2 + "  GBK  " + s2.getBytes("GBK").length);
		System.out.println(s2 + "  GB18030  " + s2.getBytes("GB18030").length);
		System.out.println(s2 + "  ISO-8859-1  " + s2.getBytes("ISO-8859-1").length);
		System.out.println(s2 + "  UTF-8  " + s2.getBytes("UTF-8").length);
		System.out.println(s2 + "  UTF-16  " + s2.getBytes("UTF-16").length);
		System.out.println(s2 + "  UTF-16BE  " + s2.getBytes("UTF-16BE").length);
		System.out.println(s2 + "  UTF-16LE  " + s2.getBytes("UTF-16LE").length);

	}

	/**
	 * 将转码后的文字写入文件，通过编辑器打开测试，确认写入的是相应编码
	 *
	 * @param bytes
	 * @throws IOException
	 */
	public void writeFile(byte[] bytes) throws IOException {
		String path = StringByteLength.class.getResource("/").getPath();
		System.out.println(path);
		String file_path = path + "charsetFile";

		File file = new File(file_path);
		if (!file.exists()) {
			file.createNewFile();
		}

		FileOutputStream out = new FileOutputStream(file);
		out.write(bytes);
		out.close();
	}
}