java常用类型转换总结

import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class ConvertType {

static String str = "30";

public static void main(String[] args){
//String--->int
int si1 = Integer.parseInt(str);
int si2 = Integer.valueOf(str);
int si3 = Integer.valueOf(str).intValue();
System.out.println(si1);
//String--->double
double sd1 = Double.parseDouble(str);
double sd2 = Double.valueOf(str);
double sd3 = Double.valueOf(str).doubleValue();
System.out.println(sd1);
//String--->float
float sf1 = Float.parseFloat(str);
float sf2 = Float.valueOf(str);
float sf3 = Float.valueOf(str).floatValue();
System.out.println(sf1);
//String--->long
long sl1 = Long.parseLong(str);
long sl2 = Long.valueOf(str);
long sl3 = Long.valueOf(str).longValue();
System.out.println(sl1);
//long、float、double、int、byte、char、short--->String
String sb = Byte.toString(new Byte("2"));
String ls = String.valueOf(30L);
String ds = Double.toString(30D);
String is = ""+30;
//String--->BigInteger
BigInteger bi = new BigInteger("30");
//BigInteger--->String
bi.toString();
//String--->byte
byte bs = Byte.parseByte("2");
//String--->long、float、double、int、byte、char、short
//   封装类.parse类型(String);
//xx--->long、float、double、int、byte、char、short、String
//   封装类.valueOf();

//String--->BigDecimal
BigDecimal bd = new BigDecimal("30.61");
//String--->double
System.out.println(bd.doubleValue());
//String--->int
System.out.println(bd.intValue());
//String--->BigInteger
System.out.println(bd.toBigInteger());

}

/**
* String--->Date
* @param str
* @param format
* @return
*/
public static Date str2Date(String str, String format) {
if (null == str || "".equals(str)) {
return null;
}
if (null == format || "".equals(format)) {
format = "yyyyMMdd";
}
SimpleDateFormat sdf = new SimpleDateFormat(format);
Date date = null;
try {
date = sdf.parse(str);
return date;
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

/**
* Date--->String
* @param date
* @param format
* @return
*/
public static String date2Str(Date date, String format) {
if (null == date) {
return null;
}
SimpleDateFormat sdf = new SimpleDateFormat(format);
return sdf.format(date);
}

}