[The Java] package type

With such data type int python is already in the class, of course, we have established the Java class encapsulates the basic data types

Java and Python but not so radical, fundamental data type in Java is not directly category

But another open stove, Create Create a class that implements one-package

Basic data types	Wrapper Class	Constructor 1	Constructor 2
int	Integer	Integer(int value)	Integer(String s)
byte	Byte	Byte(byte value)	Byte(String s)
char	Character	Character(char value)
short	Short	Short(short value)	Short(String s)
long	Long	Long(long value)	Long(String s)
float	Float	Float(double value)	Float(float value)	Float(String s)
double	Double	Double(double value)	Double(String s)
boolean	Boolean	Boolean(boolean value)	Boolean(String s)

 Boxing and unboxing

Unpacking: object classes reduced to basic data types

Packing: basic data type to the object class corresponding to

Java can be automatic packing and unpacking

Sample code:

public class T2 {
	
	public static void main(String [] args) {
		// 装箱
		int x = 10;
		Integer xx = x;
		System.out.println("xx = "+xx);
		// 拆箱
		Float f1 = new Float(3.14f);
		Float f2 = new Float(3.1415926d);
		Float f3 = new Float("3.1415926535897");
		System.out.println("f1 = "+f1);
		System.out.println("f2 = "+f2);
		System.out.println("f3 = "+f3);
		StringBuffer s = new StringBuffer("111");
		String str = s.toString();
		System.out.println("str = "+str);
		// 封装类也有toString方法，可以将其内容转成字符串
		System.out.println("f1 = "+f1.toString());
	}
}

With an encapsulation class implements two implementations string rev ideas

With the above boxing and unboxing, it may be utilized readily occur to construct a temporary anonymous data corresponding to the type of packaging objects

Then this anonymous object is assigned a basic data type parsing out

Sample code:

 

In addition, Java also provides a method of packaging parse series string class to be implemented in the basic data type conversion

 

Sample code:

public class T2 {
	
	public static void main(String [] args) {
		// 装箱
		int x = 10;
		Integer xx = x;
		System.out.println("xx = "+xx);
		// 拆箱
		Float f1 = new Float(3.14f);
		Float f2 = new Float(3.1415926d);
		Float f3 = new Float("3.1415926535897");
		System.out.println("f1 = "+f1);
		System.out.println("f2 = "+f2);
		System.out.println("f3 = "+f3);
		StringBuffer s = new StringBuffer("111");
		String str = s.toString();
		System.out.println("str = "+str);
		// 封装类也有toString方法，可以将其内容转成字符串
		System.out.println("f1 = "+f1.toString());
		// 封装类的parse方法，可以一步完成将字符换转化为基本数据类型
		String intStr = "2147483647";
		String binaryStr = "10101010101";
		int maxInt = Integer.parseInt(intStr, 10);
		int binaryInt = Integer.parseInt(binaryStr, 2);
		System.out.println(maxInt+" "+binaryInt);
	}
}

Further methods can be used to generate a binary string:

public class T2 {
	
	public static void main(String [] args) {
		// 使用包装类的toBinaryString 转二进制字符串
		String transferResult = Integer.toBinaryString(1000);
		System.out.println(transferResult);
		// 使用包装类的toHexString  转16进制字符串
		String transferResult1 = Integer.toHexString(1000);
		System.out.println(transferResult1);
		// 使用包装类的toOctString  转8进制字符串
		String transferResult2 = Integer.toOctalString(1000);
		System.out.println(transferResult2);
		
	}
}

operation result: