Java里面类型转换总结

Posted 2020-10-06

1、String 转 int

int i = Integer.valueOf(my_str).intValue();
int i = Integer.parseInt(str);

2、String 转 Integer

Integer integer = Integer.valueOf(str);

3、int 转 String

1.) String s = String.valueOf(i);
2.) String s = Integer.toString(i); 
3.) String s = "" + i; 

4、int 转 Integer

Integer integer = new Integer(i);

5、Integer 转 String

Integer integer＝String

6、Integer 转 int

int num=Integer.intValue();

7、String 转 char

char[] ca = "123".toCharArray();

8、char 转 String

String s=ca.toString();      //任何类型都可以采用toString()转换成String类型

9、日期

//日期
Calendar calendar=Calendar.getInstance();
int year=calendar.get(Calendar.YEAR);
int month=calendar.get(Calendar.MONTH)+1;
int day=calendar.get(Calendar.DATE);

//获取今天的日期字符串
String today=java.text.DateFormat.getDateInstance().format(new java.util.Date());
//获取今天的日期
new java.sql.Date(System.currentTimeMillis());

10、JAVA数据类型转换 ：

 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)//转换成时间
    {
      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);
    }
}