在Bruce Eckel的巨著《Java编程思想》中,有一个非常好的方法重载示例测试,我在此基础上稍作修改。作者非常细致,提到了一个奇怪的点:char 提升为int,而不是 byte 或 short;但是他没有说出原因!是否有人知道原因呢?
[请看testChar()方法的奇怪输出]
[请看testChar()方法的奇怪输出]
public class TypeCast {
void f1(char x) { print("f1(char) "); }
void f1(byte x) { print("f1(byte) "); }
void f1(short x) { print("f1(short) "); }
void f1(int x) { print("f1(int) "); }
void f1(long x) { print("f1(long) "); }
void f1(float x) { print("f1(float) "); }
void f1(double x) { print("f1(double) "); }
void f2(byte x) { print("f2(byte) "); }
void f2(short x) { print("f2(short) "); }
void f2(int x) { print("f2(int) "); }
void f2(long x) { print("f2(long) "); }
void f2(float x) { print("f2(float) "); }
void f2(double x) { print("f2(double) "); }
void f3(short x) { print("f3(short) "); }
void f3(int x) { print("f3(int) "); }
void f3(long x) { print("f3(long) "); }
void f3(float x) { print("f3(float) "); }
void f3(double x) { print("f3(double) "); }
void f4(int x) { print("f4(int) "); }
void f4(long x) { print("f4(long) "); }
void f4(float x) { print("f4(float) "); }
void f4(double x) { print("f4(double) "); }
void f5(long x) { print("f5(long) "); }
void f5(float x) { print("f5(float) "); }
void f5(double x) { print("f5(double) "); }
void f6(float x) { print("f6(float) "); }
void f6(double x) { print("f6(double) "); }
void f7(double x) { print("f7(double) "); }
void testConstVal() {
print("5: ");
f1(5);f2(5);f3(5);f4(5);f5(5);f6(5);f7(5); print("");
}
void testChar() {
char x = 'x';
print("char: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testByte() {
byte x = 0;
print("byte: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testShort() {
short x = 0;
print("short: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testInt() {
int x = 0;
print("int: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testLong() {
long x = 0;
print("long: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testFloat() {
float x = 0;
print("float: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void testDouble() {
double x = 0;
print("double: ");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x); print("");
}
void print(Object o) {
System.out.println(o);
}
public static void main(String[] args) {
TypeCast p = new TypeCast();
p.testConstVal();
p.testChar();
p.testByte();
p.testShort();
p.testInt();
p.testLong();
p.testFloat();
p.testDouble();
}
}
char
由2个bytes
组成。 - Patrick