Solve the problem of converting string and int in Java

This article gives you a detailed introduction to the mutual conversion between string and int in Java through example code. Friends who are interested can take a look together

int -> String

int i=12345;
String s="";

Core: s=i+"";

String -> int

s="12345";
int i;

Core:i=Integer.parseInt(s);

##

package com.fry.util;
public class Transfer {
  public void stringToInt(){
    String id="20171091";
    int n=Integer.parseInt(id);
    System.out.println(n);
  }
}

The test result of this method is 20171091 .

The following reference:

Conversion of string and int in java

1 How to convert a string String into an integer 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: Method to convert string to Double, Float, Long Much the same.

2 How to convert an integer into a string String?

A. There are three methods:

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

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

3.) String s = "" + i;

Note: Double, Float, Long The methods of converting into strings are similar.

int -> String 
int i=12345;
String s="";

The first method: s=i+"";

The second method: s=String. valueOf(i);

What is the difference between these two methods? Are the effects the same? Are they interchangeable under any circumstances?

String -> int 
s="12345";
int i;

The first method: i=Integer.parseInt(s);

The second method: i=Integer.valueOf( s).intValue();

What is the difference between these two methods? Are the effects the same? Are they interchangeable under any circumstances?

The following is the answer:

The first method: s=i+""; //will produce two String objects

The second method: s=String.valueOf(i ); //Use the static method of the String class directly to generate only one object

The first method: i=Integer.parseInt(s);//Use the static method directly and no redundant objects will be generated. But an exception will be thrown

The second method: i=Integer.valueOf(s).intValue();//Integer.valueOf(s) is equivalent to new Integer(Integer.parseInt(s)), which will also be thrown

Exception, but one more object will be generated

-------------------------------- -------------------------------------

1How to convert a string String into an integer 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 methods for converting strings into Double, Float, and Long are similar.

2 How to convert integer into word String ?

A. There are three methods:

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

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

3.) String s = "" + i;

Note: Double, Float, Long are converted into strings The methods are similar.

JAVA data type conversion

Keyword Type conversion

This is an example, talking about the conversion of data types in JAVA. Provided Everyone learns how to use common data type conversion functions in JAVA

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);
}
}

Although they can all be found in the JAVA API, organize them and make a backup.

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