> For the complete documentation index, see [llms.txt](https://heunnajo.gitbook.io/java/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://heunnajo.gitbook.io/java/java.lang-package-and-useful-class/auto-boxing-and-auto-unboxing.md).
# String to Number, String to Wrapper class
**String to Number**\
1\. Using Integer.intValue()\
2\. Using Integer.parseInt()\
3\. Using Integer.valueOf()
```java
int i = new Integer("100").intValue();
int i2 = Integer.parseInt("100");
Integer i3 = Integer.valueOf("100");
```
| String->Primitive | String->Wrapper class |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| byte b = Byte.parseByte("100");
short s = Short.parseShort("100");
int i = Integer.parseInt("100");
long l = Long.parseLong("100");
float f = Float.parseFloat("3.14");
double d = Double.parseDouble("3.14");
| Byte b = Byte.valueOf("100");
Short s = Short.valueOf("100");
Integer i = Integer.valueOf("100");
Long l = Long.valueOf("100");
Float f = Float.valueOf("3.14");
Double d = Double.valueOf("3.14");
|
n진법의 문자열을 숫자로
```java
int i4 = Integer.parseInt("100",2);//100(2)->4
int i5 = Integer.parseInt("100",8);//100(8)->64
int i6 = Integer.parseInt("100",16);//100(16)->256
int i7 = Integer.parseInt("FF",2);//FF(16)->255
//there is no "FF" in decimal.
//int i4 = Integer.parseInt("FF");error
```