public String randomString(String chars, int length) {
Random rand = new Random();
StringBuilder buf = new StringBuilder();
for (int i = 0; i < length; i++) {
buf.append(chars.charAt(rand.nextInt(chars.length())));
}
return buf.toString();
}
/**
* 获取4位随机验证码
* @return
*/
public static String getValidationCode(){
return String.valueOf((new Random().nextInt(8999) + 1000));
}
/**
* 获取6位随机验证码
* @return
*/
public static String getValidationCode(){
return String.valueOf((new Random().nextInt(899999) + 100000));
}
public class Test {
public Test() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("2010-09-11T20:00:30".replace("T", " "));
}
}
{"status":0,"message":"","bankcode":"ABOC;IBC;CCTB;ICBC"}
转换后
{\"status\":0,\"message\":\"\",\"bankcode\":\"ABOC;IBC;CCTB;ICBC\"}
package test;
public class str {
public static void main(String[] args) {
String jsonString = "{\"status\":0,\"message\":\"\",\"bankcode\":\"ABOC;IBC;CCTB;ICBC\"}";
System.out.println(jsonString);
System.out.println(jsonString.replace("\"", "\\\""));
}
}
查找特定字符并替换为找到的内容
package cn.netkiller.type;
public class ragexTest {
public ragexTest() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
String str = "<html>Netkiller</html>";
String regex = "<html>|</html>";
//运行结果返回 Netkiller
System.out.println(str.replaceAll(regex, ""));
// 运行结果返回 Neo
System.out.println("CN/NETKILLER/WWW/Neo_Chen".replaceAll(".*/(.+)_Chen", "$1"));
}
}
例如： String str = "helloword!!!"; System.out.println(str.substring(1,4)); System.out.println(str.substring(3,5)); System.out.println(str.substring(0,4)); 将得到结果为： ell lo hell
Timestamp转化为String:
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); //定义格式，不显示毫秒
Timestamp now = new Timestamp(System.currentTimeMillis());
//获取系统当前时间
String str = df.format(now);
String转化为Timestamp:
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String time = df.format(new Date());
Timestamp ts = Timestamp.valueOf(time);
java.util.Date, java.sql.Date, java.sql.Time, java.sql.Timestamp 区别
package cn.netkiller.java.date;
/**
* Hello world!
*
*/
public class App {
public static void main(String[] args) {
System.out.println("Hello World!");
// Get standard date and time
java.util.Date utilDate = new java.util.Date();
long javaTime = utilDate.getTime();
System.out.println("The Java Date is:" + utilDate.toString());
// Get and display SQL DATE
java.sql.Date sqlDate = new java.sql.Date(javaTime);
System.out.println("The SQL DATE is: " + sqlDate.toString());
// Get and display SQL TIME
java.sql.Time sqlTime = new java.sql.Time(javaTime);
System.out.println("The SQL TIME is: " + sqlTime.toString());
// Get and display SQL TIMESTAMP
java.sql.Timestamp sqlTimestamp = new java.sql.Timestamp(javaTime);
System.out.println("The SQL TIMESTAMP is: " + sqlTimestamp.toString());
}
}
The Java Date is:Thu Aug 24 16:51:57 CST 2017 The SQL DATE is: 2017-08-24 The SQL TIME is: 16:51:57 The SQL TIMESTAMP is: 2017-08-24 16:51:57.234
public static void main(String[] args) {
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
//get current date time with Date()
Date date = new Date();
System.out.println(dateFormat.format(date));
//get current date time with Calendar()
Calendar cal = Calendar.getInstance();
System.out.println(dateFormat.format(cal.getTime()));
}
Timestamp timestamp = new Timestamp(System.currentTimeMillis()); Date date = new Date(); Timestamp timestamp = new Timestamp(date.getTime());
package cn.netkiller.example;
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;
public class TimeZoneTest {
public TimeZoneTest() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
TimeZone timeZone = TimeZone.getTimeZone("Asia/Harbin");
Date date = new Date();
Timestamp timestamp = new Timestamp(date.getTime());
System.out.println(timestamp);
timestamp.setHours(timestamp.getHours()+8);
System.out.println(timestamp);
simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(simpleDateFormat.format(date));
simpleDateFormat.setTimeZone(TimeZone.getTimeZone("Asia/Harbin"));
System.out.println(simpleDateFormat.format(date));
Calendar calendar = new GregorianCalendar();
calendar.setTime(date);
calendar.setTimeZone(timeZone);
System.out.println(simpleDateFormat.format(calendar.getTime()));
}
}
package cn.netkiller.example;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class StringToDate {
public StringToDate() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = "2008-8-8 8:8:8";
try {
Date date = formatter.parse(dateString);
System.out.println(date);
System.out.println(formatter.format(date));
} catch (ParseException e) {
e.printStackTrace();
}
}
}
package cn.netkiller.example;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateCompare {
public DateCompare() {
// TODO Auto-generated constructor stub
}
public void fun1() throws InterruptedException {
Date d1 = new Date();
Thread.sleep(5000);
Date d2 = new Date();
if (d1.before(d2)) {
System.out.println(String.format("%s < %s", d1.toString(), d2.toString()));
} else {
System.out.println(String.format("%s > %s", d1.toString(), d2.toString()));
}
if (d2.after(d1)) {
System.out.println(String.format("%s > %s", d2.toString(), d1.toString()));
}
System.out.println(String.format("%s : %s => %d", d2.toString(), d1.toString(), d1.compareTo(d2)));
System.out.println(String.format("%s : %s => %d", d1.toString(), d2.toString(), d2.compareTo(d1)));
}
public void fun2() throws InterruptedException {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date1 = new Date();
Date date2 = new Date();
String s1 = dateFormat.format(date1);
String s2 = dateFormat.format(date2);
System.out.println(String.format("%s : %s => %d", s1, s2, s1.compareTo(s2)));
date1 = new Date();
Thread.sleep(5000);
date2 = new Date();
s1 = dateFormat.format(date1);
s2 = dateFormat.format(date2);
System.out.println(String.format("%s : %s => %d", s1, s2, s1.compareTo(s2)));
System.out.println(String.format("%s : %s => %d", s2, s1, s2.compareTo(s1)));
System.out.println();
}
public void fun3() throws InterruptedException, ParseException {
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm");
//Date time = formatter.parse("2016-09-27 16:29");
Date time = formatter.parse("2016-08-09 09:15");
Date startDate = formatter.parse("2016-08-09 09:15");
Date endDate = formatter.parse("2016-09-27 16:30");
if (time.before(startDate) || time.after(endDate)) {
System.out.println("Skip");
}
}
public static void main(String[] args) throws InterruptedException {
// TODO Auto-generated method stub
DateCompare dateCompare = new DateCompare();
dateCompare.fun1();
System.out.println();
dateCompare.fun2();
System.out.println();
dateCompare.fun3();
}
}
Calendar cal = Calendar.getInstance(); int year = cal.get(Calendar.YEAR); int month = cal.get(Calendar.MONTH )+1; System.out.println(year + "年 " + month + "月");
public Date getToday(String time) {
final Calendar cal = Calendar.getInstance();
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd " + time);
DateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = null;
try {
date = fmt.parse(dateFormat.format(cal.getTime()));
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}
private Date addOneDay(Date date, int day) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, day);
return cal.getTime();
}
package cn.netkiller.date;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class Yesterday {
public Yesterday() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Yesterday yesterday = new Yesterday();
System.out.println(yesterday.yesterday());
System.out.println(yesterday.getYesterday("00:00:00"));
System.out.println(yesterday.getYesterday("23:59:59"));
}
private Date yesterday() {
final Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE, -1);
return cal.getTime();
}
private Date getYesterday(String time) {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd "+time);
DateFormat fmt =new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = null;
try {
date = fmt.parse(dateFormat.format(yesterday()));
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}
}
String to Array
package cn.netkiller.java;
public class StringToArray {
public static void main(String[] args) {
// TODO Auto-generated method stub
String str="a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
String[] array = null;
array = str.split(",");
for(int i=0; i<array.length; i++){
System.out.println(array[i]);
}
}
}
public static void main(String[] args) {
try {
for (String arg : args) {
System.out.println(arg);
}
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
package cn.netkiller.java;
import java.util.Arrays;
public class ArrayToString {
public static void main(String[] args) {
String[] array = {"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
System.out.println(Arrays.toString(array));
System.out.println(Arrays.toString(array).replaceAll(", |\\[|\\]", ""));
}
}
float 不能直接做减法运算
float a = 77.22f; float b = 77.2f; System.out.println((float)a-b); System.out.println((float)a+b); 输出结果为： 0.020004272 154.42
package cn.netkiller.example;
import java.math.BigDecimal;
public class Math {
public Math() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
float a = 77.22f;
float b = 77.2f;
System.out.println((float) a + b);
System.out.println((float) a - b);
System.out.println((float) a * b);
System.out.println((float) a / b);
System.out.println("-------------");
System.out.println(add(a, b));
System.out.println(sub(a, b));
System.out.println(mul(a, b));
System.out.println(div(a, b));
}
public static float add(float v1, float v2) {
BigDecimal b1 = new BigDecimal(Float.toString(v1));
BigDecimal b2 = new BigDecimal(Float.toString(v2));
return b1.add(b2).floatValue();
}
public static float sub(float v1, float v2) {
BigDecimal b1 = new BigDecimal(Float.toString(v1));
BigDecimal b2 = new BigDecimal(Float.toString(v2));
return b1.subtract(b2).floatValue();
}
public static float mul(float v1, float v2) {
BigDecimal b1 = new BigDecimal(Float.toString(v1));
BigDecimal b2 = new BigDecimal(Float.toString(v2));
return b1.multiply(b2).floatValue();
}
public static float div(float v1, float v2) {
return div(v1, v2, 5);
}
public static float div(float v1, float v2, int scale) {
if (scale < 0) {
throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b1 = new BigDecimal(Float.toString(v1));
BigDecimal b2 = new BigDecimal(Float.toString(v2));
return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).floatValue();
}
public static float round(float v, int scale) {
if (scale < 0) {
throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b = new BigDecimal(Float.toString(v));
BigDecimal one = new BigDecimal("1");
return b.divide(one, scale, BigDecimal.ROUND_HALF_UP).floatValue();
}
}
package cn.netkiller.example;
import java.math.BigDecimal;
public class Math {
public Math() {
// TODO Auto-generated constructor stub
}
public static double add(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.add(b2).doubleValue();
}
public static double sub(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.subtract(b2).doubleValue();
}
public static double mul(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.multiply(b2).doubleValue();
}
public static double div(double v1, double v2) {
return div(v1, v2, 8);
}
public static double div(double v1, double v2, int scale) {
if (scale < 0) {
throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
}
public static double round(double v, int scale) {
if (scale < 0) {
throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b = new BigDecimal(Double.toString(v));
BigDecimal one = new BigDecimal("1");
return b.divide(one, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
}
}
package cn.netkiller.example;
import java.math.BigDecimal;
public class BigDecimalTest {
public BigDecimalTest() {
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
BigDecimal first = new BigDecimal("1.0");
BigDecimal second = new BigDecimal("1.77");
System.out.println(String.format("%s, %s", first, second));
if (first.equals(second))
System.out.println("equals: true");
else
System.out.println("equals: false");
if (first.compareTo(second) == 0)
System.out.println("compareTo: true");
else
System.out.println("compareTo: false");
BigDecimal zero = new BigDecimal("0");
BigDecimal one = new BigDecimal("1");
BigDecimal minus = new BigDecimal("-1");
if (zero.compareTo(one) < 0)
System.out.println("比較演算子[ < ]: true");
if (one.compareTo(one) == 0)
System.out.println("比較演算子[ == ]: true");
if (zero.compareTo(minus) > 0)
System.out.println("比較演算子[ > ]: true");
if (zero.compareTo(minus) >= 0)
System.out.println("比較演算子[ >= ]: true");
if (zero.compareTo(minus) != 0)
System.out.println("比較演算子[ != ]: true");
if (zero.compareTo(one) <= 0)
System.out.println("比較演算子[ <= ]: true");
}
}
class EnumExample1{
public enum Season { WINTER, SPRING, SUMMER, FALL }
public static void main(String[] args) {
for (Season s : Season.values())
System.out.println(s);
}
}
原文出处：Netkiller 系列 手札
本文作者：陈景峯
转载请与作者联系，同时请务必标明文章原始出处和作者信息及本声明。
