To set the default file.encoding in a JVM you could set it in the JVM startup as -Dfile.encoding=UTF-8 or in JAVA_TOOLS_OPTIONS with the same part. But if you want to set it programmatically after the JVM already started?
A System.setProperty("file.encoding", "UTF-16"); will only set the file.encoding property. All other classes which rely on the defaultCharset, like all Streams and Buffers won't recognize that change. Here is a Junit Test, which shows you how to reset the Charset.defaultCharset field:
package de.kambrium;
import java.lang.reflect.Field;
import java.nio.charset.Charset;
import org.junit.Before;
import org.junit.Test;
public class CharsetTest {
@Before
public void setUp() throws Exception {
}
@Test
public void test() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
dump("Actual system config");
System.setProperty("file.encoding", "UTF-16");
dump("Config after System.setProperty(\"file.encoding\", \"UTF-16\")");
Field cs = Charset.class.getDeclaredField("defaultCharset");
cs.setAccessible(true);
cs.set(null, null);
dump("Config after manipulating defatulCharset field");
}
private void dump(String msg) {
System.out.println(msg);
System.out.println("****************************************************************");
System.out.println("file.encoding = " + System.getProperty("file.encoding"));
System.out.println("defaultCharset = " + Charset.defaultCharset());
System.out.println("****************************************************************");
System.out.println("");
}
}
Output will look like this
Actual system config
****************************************************************
file.encoding = UTF-8
defaultCharset = UTF-8
****************************************************************
Config after System.setProperty("file.encoding", "UTF-16")
****************************************************************
file.encoding = UTF-16
defaultCharset = UTF-8
****************************************************************
Config after manipulating defatulCharset field
****************************************************************
file.encoding = UTF-16
defaultCharset = UTF-16
****************************************************************