println

public void println(Object x) {
String s = String.valueOf(x);
if (getClass() == PrintStream.class) {
// need to apply String.valueOf again since first invocation
// might return null
writeln(String.valueOf(s));
} else {
synchronized (this) {
print(s);
newLine();
}
}
}

public static String valueOf(Object obj) {
return (obj == null) ? “null” : obj.toString();
}

java.lang java.util

java.lang says: Provides classes that are fundamental to the design of the Java programming language（基础包）

java - util :stands** for utility and contains utility classes.(工具包，实用包)