Here you can find the source of toString(Date date, String format)
public static String toString(Date date, String format)
//package com.java2s; import java.sql.Date; import java.sql.Time; import java.text.*; public class Main { public static final String DEFAULT_DATE_YMD_FORMAT = "yyyy-MM-dd"; public static final String DEFAULT_TIME_FORMAT = "HH:mm:ss"; public static String toString(Date date) { return toString((java.util.Date) date); }// w ww . j av a 2s . c o m public static String toString(java.util.Date date) { return toString(date, DEFAULT_DATE_YMD_FORMAT); } public static String toString(Date date, String format) { return toString((java.util.Date) date, format); } public static String toString(java.util.Date date, String format) { if (date == null) { return null; } if (format == null) { throw new IllegalArgumentException("The value of an argument is inaccurate."); } SimpleDateFormat sdf = new SimpleDateFormat(format); return sdf.format(date); } public static String toString(Time time, String format) { if (time == null) { return null; } if (format == null) { throw new IllegalArgumentException("The value of an argument is inaccurate."); } SimpleDateFormat sdf = new SimpleDateFormat(format); return sdf.format(time); } public static String toString(Time time) { return toString(time, DEFAULT_TIME_FORMAT); } }