Data type conversions in Java

1. String to int?

A. There are two methods:

1). int i = Integer.parseint ([String]); or
i = Integer.parseint ([string],[int radix]);

2). int i = integer.valueof (my_str). Intvalue ();

Note: The string is converted to Double, Float, and Long in a similar way.

2 How do I convert an integer int to a string string?

A. there are three ways:

1.) String s = string.valueof (i);

2.) String s = integer.tostring (i);

3.) String s = "" + I;

Note: Double, Float, Long turn into a string in a similar way.

JAVA Data type Conversions
Keyword type conversions
SOURCE

This is an example of the conversion of data numbers in Java. For everyone to learn

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 Common data type conversion functions in
Although all can be found in the Java API, tidy up to make a backup.

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)

++++++++++++++++++++++++++++++++++++++++++++++++++++++

Data type

There are four basic types of the following:
int The length data types are: Byte (8bits), short (16bits), int (32bits), Long (64bits) ,
float length data types are: Single precision (32bits float), double precision (64bits double)
Boolean the values of type variables are: ture, false
Char data types are: Unicode characters, 16-bit
Corresponding class types: Integer, Float, Boolean, Character, Double, short, Byte, Long

Conversion principles

Convert from low precision to high precision
byte , short, int, long, float, double, Char
Note: Two char operations are automatically converted to int, and when char and other types are operated, they are automatically converted to int, and then other types of auto-conversions

Basic type conversion to class type

Forward conversion: A new class-type variable with a class wrapper
Integer a= new Integer (2);
Reverse conversions: Converting through a class wrapper
int B=a.intvalue ();

class type to string conversion

forward Conversions: Because each class is a subclass of the object class, and all object classes have a ToString () function, the ToString () function can be converted to
Reverse Conversions: A new class-type variable is created from the class wrapper
Eg1:int i=integer.valueof ("123"). Intvalue ()
Note: The previous example converts a string into an integer object, and then calls the object's Intvalue () method to return its corresponding int value.
eg2:float f=float.valueof ("123"). Floatvalue ()
Note: The previous example converts a string into a float object and then calls the object's Floatvalue () method to return its corresponding float value.
Eg3:boolean b=boolean.valueof ("123"). Booleanvalue ()
Note: The previous example converts a string into a Boolean object and then calls the object's Booleanvalue () method to return its corresponding Boolean value.
eg4:double d=double.valueof ("123"). Doublevalue ()
Note: The previous example converts a string into a double object, and then calls the object's Doublevalue () method to return its corresponding double value.
Eg5:long l=long.valueof ("123"). Longvalue ()
Note: The previous example converts a string into a long object, and then calls the object's Longvalue () method to return its corresponding long value.
eg6:char=character.valueof ("123"). Charvalue ()
Note: The previous example converts a string into a character object, and then calls the object's Charvalue () method to return its corresponding char value.

Conversion of a primitive type to a string
Forward conversions:
such as: int a=12;
String b;b=a+ "";

Reverse Conversions:
through the class wrapper
eg1:int i=integer.parseint ("123")
Description: This method can only be used to convert a string into an integer variable
eg2:float f=float.valueof ("123"). Floatvalue ()
Note: The previous example converts a string into a float object and then calls the object's Floatvalue () method to return its corresponding float value.
Eg3:boolean b=boolean.valueof ("123"). Booleanvalue ()
Note: The previous example converts a string into a Boolean object and then calls the object's Booleanvalue () method to return its corresponding Boolean value.
eg4:double d=double.valueof ("123"). Doublevalue ()
Note: The previous example converts a string into a double object, and then calls the object's Doublevalue () method to return its corresponding double value.
eg5:long l=long.valueof ("123"). Longvalue ()
Note: The previous example converts a string into a long object, and then calls the object's Longvalue () method to return its corresponding long value.
Eg6:char=character.valueof ("123"). Charvalue ()
Note: The previous example converts a string into a character object, and then calls the object's Charvalue () method to return its corresponding char value

Transferred from: http://blog.csdn.net/xiaosan1987925/article/details/3245270

Data type conversions in Java