java编程思想练习题-第2章练习9

题目：编写一个程序，展示自动包装功能对所有的基本类型和包装器类型都起作用。

public class test {
	public static void main(String[] args) {
		boolean b = false;
		char c = 'x';
		byte t = 8;
		short s = 16;
		int i = 32;
		long l = 64;
		float f = 0.32f;
		double d = 0.64;
		Boolean B = b;
		System.out.println("boolean b = " + b); 		
		System.out.println("Boolean B = " + B); 
		Character C = c;
		System.out.println("char c = " + c);
		System.out.println("Character C = " + C);
		Byte T = t;
		System.out.println("byte t = " + t);
		System.out.println("Byte T = " + T);
		Short S = s;
		System.out.println("short s = " + s);
		System.out.println("Short S = " + S);
		Integer I = i;
		System.out.println("int i = " + i);
		System.out.println("Integer I = " + I);
		Long L = l;
		System.out.println("long l = " + l);
		System.out.println("Long L = " + L);
		Float F = f;
		System.out.println("float f = " + f);
		System.out.println("Float F = " + F);
		Double D = d;
		System.out.println("double d = " + d);
		System.out.println("Double D = " + D);		
	}
}

 结果：

boolean b = false
Boolean B = false
char c = x
Character C = x
byte t = 8
Byte T = 8
short s = 16
Short S = 16
int i = 32
Integer I = 32
long l = 64
Long L = 64
float f = 0.32
Float F = 0.32
double d = 0.64
Double D = 0.64

 结论：把基本类型赋值给对应的包装类型可行，是因为java自动装箱机制的存在。同理，自动拆箱使得反之亦然