type assertion：类型断言
适用于 interface{}; 将 interface{}转换为具体类型；可能会失败
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var a interface{} = 100;
value,ok := a.(int)
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convertion: 类型转换
only for numerical type
1. widening conversion(implict conversion)
go dont’s support
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class Test
{
public static void main(String[] args)
{
int i = 100;
// automatic type conversion
long l = i;
// automatic type conversion
float f = l;
System.out.println("Int value "+i);
System.out.println("Long value "+l);
System.out.println("Float value "+f);
}
}
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2. narrowing conversion(explicit conversion)
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class Test
{
public static void main(String[] args)
{
double d = 100.04;
//explicit type casting
long l = (long)d;
//explicit type casting
int i = (int)l;
System.out.println("Double value "+d);
//fractional part lost
System.out.println("Long value "+l);
//fractional part lost
System.out.println("Int value "+i);
}
}
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for go
in go, it dosen’t matter if the type widen or narrow, its conversion must be explict;s
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var a int = b;
var b float64 = float64(a)
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