Is multi-thread output from System.out.println interleaved

Question

If multiple threads call System.out.println(String) without synchronization, can the output get interleaved? Or is the write of each line atomic? The API makes no mention of

Answer 1

The OpenJDK source code answers your question:

public void println(String x) {
    synchronized (this) {
        print(x);
        newLine();
    }
}

Reference: http://hg.openjdk.java.net/jdk6/jdk6/jdk/file/39e8fe7a0af1/src/share/classes/java/io/PrintStream.java