JVM编码 - 阿甘的博客 | Arganzheng's Blog

package java.nio.charset;

public abstract class Charset implements Comparable<Charset>{

    private static volatile Charset defaultCharset;


    /**
     * Returns the default charset of this Java virtual machine.
     *
     * <p> The default charset is determined during virtual-machine startup and
     * typically depends upon the locale and charset of the underlying
     * operating system.
     *
     * @return  A charset object for the default charset
     *
     * @since 1.5
     */
    public static Charset defaultCharset() {
        if (defaultCharset == null) {
	    synchronized (Charset.class) {
		java.security.PrivilegedAction pa =
		    new GetPropertyAction("file.encoding");
		String csn = (String)AccessController.doPrivileged(pa);
		Charset cs = lookup(csn);
		if (cs != null)
		    defaultCharset = cs;
                else 
		    defaultCharset = forName("UTF-8");
            }
	}
	return defaultCharset;
    }

}

就是一个lazy-init的单例模式实现。另外，其实就是取自file.encoding环境变量，取不到，默认是”UTF-8”。

Tips 可以在eclipse中用Display View中，执行java语句：

System.getProperty("file.encoding");

非常实用的功能。

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