Java String到int，Java int到String

Today we will look at Java String to int conversion and then java int to String conversion. Java provides several ways to convert String to int and int to String.

今天，我们将看一下Java String到int的转换，然后是java int到String的转换。 Java提供了几种将String转换为int以及将int转换为String的方法。

Java字符串到int (Java String to int)

Using Integer.parseInt method使用Integer.parseInt方法
Using Integer.valueOf method使用Integer.valueOf方法
Using above methods with different radix.使用上述方法使用不同的基数。

Java String to int示例 (Java String to int example)

Let’s write a simple java program to convert String to an int, note that String is an Object whereas int is a primitive data type. An integer can be written in Decimal, Hexadecimal, Octal Binary or any other nonstandard formats.

让我们编写一个简单的Java程序将String转换为int，注意String是一个Object，而int是原始数据类型。整数可以十进制，十六进制，八进制二进制或任何其他非标准格式写入。

Java 7 one of the feature is Binary Literals. In this example, we will explore how to convert String to int using different radix values.

Java 7的功能之一是Binary Literals 。在此示例中，我们将探讨如何使用不同的基数值将String转换为int。

package com.journaldev.string;public class JavaStringToInt {public static void main(String[] args) {String str = "10";int x = Integer.parseInt(str);System.out.println("Java String to int value using Integer.parseInt() = "+x);int y = Integer.valueOf(str);System.out.println("Java String to int value using Integer.valueOf() = "+y);String binary = "0100"; //4int a = Integer.valueOf(binary, 2);int b = Integer.parseInt(binary, 2);System.out.println("Java Binary String to int value = "+a);System.out.println("Java Binary String to int value = "+b);String octal = "0100"; //64int c = Integer.valueOf(octal, 8);int d = Integer.parseInt(octal, 8);System.out.println("Java Octal String to int value = "+c);System.out.println("Java Octal String to int value = "+d);String hexadecimal = "0100"; //256int e = Integer.valueOf(hexadecimal, 16);int f = Integer.parseInt(hexadecimal, 16);System.out.println("Java hexadecimal String to int value = "+e);System.out.println("Java hexadecimal String to int value = "+f);String customRadix = "0100"; //25int g = Integer.valueOf(customRadix, 5);int h = Integer.parseInt(customRadix, 5);System.out.println("Java String with radix 5 to int value = "+g);System.out.println("Java String with radix 5 to int value = "+h);}}

Output of the above program is:

上面程序的输出是：

Java String to int value using Integer.parseInt() = 10
Java String to int value using Integer.valueOf() = 10
Java Binary String to int value = 4
Java Binary String to int value = 4
Java Octal String to int value = 64
Java Octal String to int value = 64
Java hexadecimal String to int value = 256
Java hexadecimal String to int value = 256
Java String with radix 5 to int value = 25
Java String with radix 5 to int value = 25

Interegr.parseInt(String str) is the most commonly used method to convert String to int, if String represents int in decimal format. Internally, it invokes method Interegr.parseInt(String str, int radix) with radix value as 10.如果String以十进制格式表示int，则Interegr.parseInt(String str)是将String转换为int的最常用方法。在内部，它调用方法Interegr.parseInt(String str, int radix) ，基数为10。
By passing redix value as 2, we can convert Binary int representation String to int, same is true for other known formats Octal, Hexadecimal also.通过将redix值传递为2，我们可以将Binary int表示形式的String转换为int，对于其他已知格式Octal，十六进制也是如此。
Minimum radix value is 2 and maximum radix value is 36. For radix 36, it includes 0 to 9 and then A(10) to Z(36). The conversion from String to int is case insensitive.最小基数为2，最大基数为36。对于基数36，它包括0到9，然后包括A（10）到Z（36）。从String到int的转换不区分大小写。
Integer.valueOf(String str) is also a way to convert String to int. There is also an overloaded method where we can pass radix, as you can see from above example code.Integer.valueOf(String str)也是一种将String转换为int的方法。从上面的示例代码可以看到，还有一个重载的方法可以传递基数。
If the String representation does not contain a parsable integer, both above methods throw NumberFormatException.如果String表示形式不包含可分析的整数，则上述两种方法都将引发NumberFormatException 。
The String representation should only contain the value and not the radix prefix associated with int, like 0x, 0b etc.字符串表示形式应仅包含值，而不应包含与int相关联的基数前缀，例如0x，0b等。

Java int转换为String (Java int to String)

Using + operator to concatenate int to string.使用+运算符将int连接到字符串。
Using String.valueOf method.使用String.valueOf方法。
Using String.format method使用String.format方法

Java int到String的示例 (Java int to String example)

Let’s write a simple program to convert java int to String object using different methods.

让我们编写一个简单的程序，使用不同的方法将java int转换为String对象。

package com.journaldev.string;public class JavaIntToString {public static void main(String[] args) {int i = 10;int j = 0xEF;int k = 0123;int l = 0b111;String str = "" + i;String str1 = String.valueOf(j);String str2 = String.format("%d", k);String str3 = "" + l;System.out.println(i + " decimal int to String " + str);System.out.println(j + " hexadecimal int to String " + str1);System.out.println(k + " octal int to String " + str2);System.out.println(l + " binary int to String " + str3);}}

The output of the above program is:

上面程序的输出是：

10 decimal int to String 10
239 hexadecimal int to String 239
83 octal int to String 83
7 binary int to String 7

“+” operator is overloaded for String and it can be used to convert int to String. It also takes care of different formats like Hexadecimal, Octal, Binary and convert them to decimal format before returning the final String object.String的“ + ”运算符已重载，可用于将int转换为String。它还照顾不同的格式，例如十六进制，八进制，二进制，并在返回最终的String对象之前将它们转换为十进制格式。
String.valueOf(int i) can be used to convert int to String. valueOf() method is overloaded to accept float, long, double etc. Internally it uses Integer.toString(int i) method to return the String object.String.valueOf(int i)可用于将int转换为String。 valueOf()方法已重载以接受float，long，double等。在内部，它使用Integer.toString(int i)方法返回String对象。
String.format(String format, Object... args) is also another way to convert int to String object.String.format(String format, Object... args)也是将int转换为String对象的另一种方法。
Before converting int to string, value is always converted to decimal format and then assigned to string. As you can see from the output above, all the string representations are in the decimal format.在将int转换为字符串之前，值始终会转换为十进制格式，然后再分配给字符串。从上面的输出中可以看到，所有的字符串表示形式都是十进制格式。

That’s all for Java String to int and int to String conversion, we will cover more java interview questions in future posts.

Java字符串到int以及从int到String的转换就这些了，我们将在以后的文章中介绍更多Java面试问题。

Reference: Integer API Doc

参考： Integer API文档

翻译自: https://www.journaldev.com/727/java-string-int