自动数据类型提升的运算
byte 、char、short 、int 、long 、float、double
注意：当byte、char、short 三种数据类型做运算，结果为int型
代码1
class VariableTest1
{
public static void main(String[] args)
{
byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
}
}
---------- java ----------
263
输出完成 (耗时 0 秒) - 正常终止
示例2
class VariableTest1
{
public static void main(String[] args)
{
byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
float f = y + r;
System.out.println(f);
short s1 = 123;
int d1 = s1;
System.out.println(d1);
}
}
---------- java ----------
263
263.0
123
输出完成 (耗时 0 秒) - 正常终止
示例3强制类型转换
class VariableTest1
{
public static void main(String[] args)
{
/*byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
float f = y + r;
System.out.println(f);
short s1 = 123;
int d1 = s1;
System.out.println(d1);
*/
double g1 = 12.9;
int i1 = (int)g1; //截断操作
System.out.println(i1);
}
}
---------- java ----------
12
输出完成 (耗时 0 秒) - 正常终止
long转换short型转换操作
class VariableTest1
{
public static void main(String[] args)
{
/*byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
float f = y + r;
System.out.println(f);
short s1 = 123;
int d1 = s1;
System.out.println(d1);
double g1 = 12.9;
int i1 = (int)g1;
System.out.println(i1);
*/
long l1 = 123;
short s2 = (short)l1;
System.out.println(s2);
}
}
---------- java ----------
123
输出完成 (耗时 0 秒) - 正常终止
示例2
class VariableTest1
{
public static void main(String[] args)
{
int i2 = 128;
byte b2 = (byte)i2;
System.out.println(b2);
}
}
---------- java ----------
-128
输出完成 (耗时 0 秒) - 正常终止
编码特殊情况
class VariableTest1
{
public static void main(String[] args)
{
long i1 = 123456;//正常long型数据数值后应添加L或者l;不加也正常；因为没加的话表示自动类型提升操作；默认是int 有赋值给long型
System.out.println(i1);
long l1 = 12345678998; // 因为没加L而它的数值int有放不下所有报错
System.out.lprintln(l1);
}
}
---------- javac ----------
VariableTest1.java:35: 错误: 过大的整数: 12345678998
long l1 = 12345678998;
^
1 个错误
输出完成 (耗时 0 秒) - 正常终止
示例
class VariableTest1
{
public static void main(String[] args)
{
/*byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
float f = y + r;
System.out.println(f);
short s1 = 123;
int d1 = s1;
System.out.println(d1);
double g1 = 12.9;
int i1 = (int)g1;
System.out.println(i1);
long l1 = 123;
short s2 = (short)l1;
int i2 = 128;
byte b2 = (byte)i2;
System.out.println(b2);
*/
//
long i1 = 123456;//正常long型数据数值后应添加L或者l;不加也正常；没加的话表示自动类型提升操作；默认是int 有赋值给long型
System.out.println(i1);
long l1 = 12345678998l;
System.out.println(l1);
}
}
常量编码；
class VariableTest1
{
public static void main(String[] args)
{
//整型常量默认类型int型；
//浮点型常量默认是double型；
byte q = 12;
byte b1 = q + 1;
System.out.println(b1);
}
}
---------- javac ----------
VariableTest1.java:38: 错误: 不兼容的类型: 从int转换到byte可能会有损失
byte b1 = q + 1;
^
1 个错误
输出完成 (耗时 1 秒) - 正常终止
class VariableTest1
{
public static void main(String[] args)
{
/*byte y = 9;
int r = 254;
int e = y+r;
System.out.println(e);
float f = y + r;
System.out.println(f);
short s1 = 123;
int d1 = s1;
System.out.println(d1);
double g1 = 12.9;
int i1 = (int)g1;
System.out.println(i1);
long l1 = 123;
short s2 = (short)l1;
int i2 = 128;
byte b2 = (byte)i2;
System.out.println(b2);
*/
//
//long i1 = 123456;//正常long型数据数值后应添加L或者l;不加也正常；没加的话表示自动类型提升操作；默认是int 有赋值给long型
//System.out.println(i1);
//long l1 = 12345678998l;
//System.out.println(l1);
byte q = 12;
byte b1 = q + 1;// 编译失败
System.out.println(b1);
float f1 = b + 12.3;// 编译失败
System.out.println(f1);
}
}