JAVA中的类型转换

1如何将字串 String 转换成整数 int?

A. 有两个方法:

1). int i = Integer.parseInt([String]); 或
i = Integer.parseInt([String],[int radix]);

2). int i = Integer.valueOf(my_str).intValue();

注: 字串转成 Double, Float, Long 的方法大同小异.


2 如何将整数 int 转换成字串 String ?


A. 有叁种方法:

1.) String s = String.valueOf(i);

2.) String s = Integer.toString(i);

3.) String s = "" + i;

注: Double, Float, Long 转成字串的方法大同小异.

 

package com.sdjt.study.leixingzhuanhuan;    

import java.text.ParseException;

/**  
 * @author:lyy
 * @version 创建时间：2009-8-7 下午07:04:09  
 * 类说明  
 */
public class Test {

	public static void main(String[] args) throws ParseException {
	
		/**
		 * String与int的转换
		 */
		String str = "123";
		int i = Integer.parseInt(str);//String 转换成int
		int j = Integer.valueOf(str).intValue();//String 转换成int
		System.out.println(i);
		System.out.println(j);
		String str1 = "" + i;//int转换成String
		String str2 = String.valueOf(i);//int转换成String
		String str3 = Integer.toString(j);//int转换成String
		System.out.println(str1);
		System.out.println(str2);
		System.out.println(str3);
		/**
		 * Sting与Date的转换
		 */
		String date = "2009-08-26";//今天是七夕节
		String date1 = null;
		//取得当前时间
		java.util.Calendar c = java.util.Calendar.getInstance();
		java.util.Date nowDate = new java.util.Date();
		nowDate = c.getTime();
		System.out.println(nowDate);
		java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-dd");
		date1 = format.format(nowDate);//Date类型转换成String类型
		System.out.println(date1);
		java.util.Date dateQX = format.parse(date);//String 转换成 Date 抛出ParseException异常
		System.out.println(dateQX);
		/**
		 * Sting与Calendar的转换
		 */
		java.util.Calendar today = java.util.Calendar.getInstance();
//		System.out.println(today);
		java.util.Calendar date3 = null;
		String date2 = "2009-08-27";
		int year = Integer.parseInt(date2.substring(0, 4));
		int month = Integer.parseInt(date2.substring(5,7));
		int day = Integer.parseInt(date2.substring(8,10));
		date3.set(year, month, day);//String 类型转换成 Calendar类型
//		System.out.println(date3);
		date3.set(year, month-1, day);
//		System.out.println(date3);
		
		String date4 = null;
		date4 = format.format(today.getTime());//Calendar类型转换成String类型
		System.out.println(date4);
	}
	
}

 

这是一个例子,说的是JAVA中数据数型的转换

package cn.com.lwkj.erts.register; 
import java.sql.Date; 
public class TypeChange { 
public TypeChange() { 
} 
//change the string type to the int type 
public static int stringToInt(String intstr) 
{ 
Integer integer; 
integer = Integer.valueOf(intstr); 
return integer.intValue(); 
} 
//change int type to the string type 
public static String intToString(int value) 
{ 
Integer integer = new Integer(value); 
return integer.toString(); 
} 
//change the string type to the float type 
public static float stringToFloat(String floatstr) 
{ 
Float floatee; 
floatee = Float.valueOf(floatstr); 
return floatee.floatValue(); 
} 
//change the float type to the string type 
public static String floatToString(float value) 
{ 
Float floatee = new Float(value); 
return floatee.toString(); 
} 
//change the string type to the sqlDate type 
public static java.sql.Date stringToDate(String dateStr) 
{ 
return java.sql.Date.valueOf(dateStr); 
} 
//change the sqlDate type to the string type 
public static String dateToString(java.sql.Date datee) 
{ 
return datee.toString(); 
} 

public static void main(String[] args) 
{ 
java.sql.Date day ; 
day = TypeChange.stringToDate("2003-11-3"); 
String strday = TypeChange.dateToString(day); 
System.out.println(strday); 
} 


} 

 JAVA中常用数据类型转换函数
虽然都能在JAVA API中找到，整理一下做个备份。

string->byte
Byte static byte parseByte(String s)

byte->string
Byte static String toString(byte b)

char->string
Character static String to String (char c)

string->Short
Short static Short parseShort(String s)

Short->String
Short static String toString(Short s)

String->Integer
Integer static int parseInt(String s)

Integer->String
Integer static String tostring(int i)

String->Long
Long static long parseLong(String s)

Long->String
Long static String toString(Long i)

String->Float
Float static float parseFloat(String s)

Float->String
Float static String toString(float f)

String->Double
Double static double parseDouble(String s)

Double->String
Double static String toString(Double s)