// API is backwards-compatible with android.util.Log, so you already know it.
Log.d(tag, "X equals " + x);

// Safe logging for multiple comma-separated values
Log.d(tag, "X", x)

// Tag is optional, by default it equals to the class name 
class Foo {
	public void foo() {
		Log.d("Hello"); // prints 'D/Foo: Hello'
	}
}

// If tag or TAG field is found - it overrides the class name
class Foo {
	private final static String tag = "Bar";
	public void foo() {
		Log.d("Hello"); // prints 'D/Bar: Hello'
	}
}

// And it's still compatible with your old code
class Foo {
	private final static String TAG = "Bar";
	public void foo() {
		Log.d(TAG, "Hello"); // prints 'D/Bar: Hello', not 'D/Bar: Bar Hello'
	}
}

// Even if you used different tag field names
class Foo {
	static {
		Log.useTags(new String[]{"tag", "TAG", "MYTAG", "_TAG", "iLoveLongFieldName"});
	}
	private final static String _TAG = "Bar";
	...
}

// Support for Throwables
Exception e = new Exception("foo");
Log.d("Something bad happened", someObject, "error:", e); // A log message and a stack trace will be printed

// Chainable API
Log
	.d("First")
	.d("Second")
	.d("Third line")

// Filters by log level
Log.level(Log.I);
Log.d("foo"); // will be ignored

// Format strings are suported, too
Log.useFormat(true);
Log.d("X equals %d", x); // prints 'X equals 42'
// But if no format is provided - log will be printed as multiple values
Log.d("Value of X", x); // prints 'Value of X 42'

// Long messages are wrapped on newlines
// If the message doesn't contain newlines and is longer than 4000 symbols
// (like compact JSONs or HTML) - it will be wrapped on whitespace or punctuation
Log.d("Hello\nworld"); // prints 'D/SomeTag: Hello' and 'D/SomeTag: world'

// On Android logs are printed via android.util.Log by default.
// On other JVMs logs are printed via System.out.println by default.
// Unless specified otherwise
Log.usePrinter(Log.SYSTEM, true).usePrinter(Log.ANDROID, false).d("hello"); // will be printed via System.out on Android as well
Log.usePrinter(mMyPrinter, true); // or you can use your own custom printers

// If you want to disable debug printing for Release build
if (!BuildConfig.DEBUG) {
  Log.usePrinter(Log.ANDROID, false); // from now on Log.d etc do nothing and is likely to be optimized with JIT
}

// And it's only a single class of 200 LOC, so don't be afraid that it will
// bloat your APK or slow down your builds.