Question

Which of the following ways is better to convert Integer, Double to String in Java.

String.valueOf(doubleVal)
doubleVal + ""
doubleVal.toString()

Thanks.

Answer 1

doubleVal + "" is most likely the worst since it has to do a concatanation with an empty string. However, the other two are equivalent. The source code from OpenJDK:

// java.lang.String
public static String valueOf(double d) {
    return Double.toString(d);
}

// java.lang.Double
public static String toString(double d) {
    return new FloatingDecimal(d).toJavaFormatString();
}