### [重载与基本类型](https://lingcoder.gitee.io/onjava8/#/book/06-Housekeeping?id=%e9%87%8d%e8%bd%bd%e4%b8%8e%e5%9f%ba%e6%9c%ac%e7%b1%bb%e5%9e%8b) 基本类型可以自动从较小的类型转型为较大的类型。当这与重载结合时，这会令人有点困惑，下面是一个这样的例子： ~~~ // housekeeping/PrimitiveOverloading.java // Promotion of primitives and overloading public class PrimitiveOverloading { void f1(char x) { System.out.print("f1(char)"); } void f1(byte x) { System.out.print("f1(byte)"); } void f1(short x) { System.out.print("f1(short)"); } void f1(int x) { System.out.print("f1(int)"); } void f1(long x) { System.out.print("f1(long)"); } void f1(float x) { System.out.print("f1(float)"); } void f1(double x) { System.out.print("f1(double)"); } void f2(byte x) { System.out.print("f2(byte)"); } void f2(short x) { System.out.print("f2(short)"); } void f2(int x) { System.out.print("f2(int)"); } void f2(long x) { System.out.print("f2(long)"); } void f2(float x) { System.out.print("f2(float)"); } void f2(double x) { System.out.print("f2(double)"); } void f3(short x) { System.out.print("f3(short)"); } void f3(int x) { System.out.print("f3(int)"); } void f3(long x) { System.out.print("f3(long)"); } void f3(float x) { System.out.print("f3(float)"); } void f3(double x) { System.out.print("f3(double)"); } void f4(int x) { System.out.print("f4(int)"); } void f4(long x) { System.out.print("f4(long)"); } void f4(float x) { System.out.print("f4(float)"); } void f4(double x) { System.out.print("f4(double)"); } void f5(long x) { System.out.print("f5(long)"); } void f5(float x) { System.out.print("f5(float)"); } void f5(double x) { System.out.print("f5(double)"); } void f6(float x) { System.out.print("f6(float)"); } void f6(double x) { System.out.print("f6(double)"); } void f7(double x) { System.out.print("f7(double)"); } void testConstVal() { System.out.print("5: "); f1(5);f2(5);f3(5);f4(5);f5(5);f6(5);f7(5); System.out.println(); } void testChar() { char x = 'x'; System.out.print("char: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testByte() { byte x = 0; System.out.print("byte: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testShort() { short x = 0; System.out.print("short: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testInt() { int x = 0; System.out.print("int: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testLong() { long x = 0; System.out.print("long: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testFloat() { float x = 0; System.out.print("float: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } void testDouble() { double x = 0; System.out.print("double: "); f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); System.out.println(); } public static void main(String[] args) { PrimitiveOverloading p = new PrimitiveOverloading(); p.testConstVal(); p.testChar(); p.testByte(); p.testShort(); p.testInt(); p.testLong(); p.testFloat(); p.testDouble(); } } ~~~ 输出： ~~~ 5: f1(int)f2(int)f3(int)f4(int)f5(long)f6(float)f7(double) char: f1(char)f2(int)f3(int)f4(int)f5(long)f6(float)f7(double) byte: f1(byte)f2(byte)f3(short)f4(int)f5(long)f6(float)f7(double) short: f1(short)f2(short)f3(short)f4(int)f5(long)f6(float)f7(double) int: f1(int)f2(int)f3(int)f4(int)f5(long)f6(float)f7(double) long: f1(long)f2(long)f3(long)f4(long)f5(long)f6(float)f7(double) float: f1(float)f2(float)f3(float)f4(float)f5(float)f6(float)f7(double) double: f1(double)f2(double)f3(double)f4(double)f5(double)f6(double)f7(double) ~~~ 如果传入的参数类型大于方法期望接收的参数类型，你必须首先做下转换，如果你不做的话，编译器就会报错。