为什么将printf(“%s”)用于传递给泛型方法的参数? [英] Why use printf("%s") for arguments passed to generic methods?
问题描述
package genericMethods;
public class OverloadedMethods {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Integer[] integerArray = {1, 2, 3, 4, 5};
Double[] doubleArray = {1.0, 2.0, 3.0, 4.0, 5.0};
Character[] charArray = {'a', 'b', 'c', 'd'};
System.out.println("A has: ");
printArray(integerArray);
System.out.println("B has: ");
printArray(doubleArray);
System.out.println("C has: ");
printArray(charArray);
}
public static <T> void printArray(T[] array)
{
for(T element : array)
System.out.printf("%s ", element);//why use %s instead of others?
System.out.println();
}
}
我的问题是方法printArray( )不知道打印出什么类型的数据,并且似乎%d将在运行时发生错误 - 但不仅仅是String的%s?
My question is the method printArray() doesn't know what type of data is going to print out, and seems %d will occur error at run time - but isn't %s for String only ?
推荐答案
问题在于你不知道元素的类型。在您的示例中,它可以是Integer,Double或Character。在这种情况下,您不能使用%d或%lf,因为这些不适用于非Integer(对于%d)或Double(对于%lf)的类型。
The issue is that you don't KNOW what type "element" will be. In your example, it could be Integer, Double, or Character. That being the case, you can't use %d or %lf, because those wouldn't work for types that aren't Integer (for %d) or Double (for %lf).
%s实际上适用于所有人,因为所有对象类型都有.toString(),所以它们都可以转换为字符串进行打印。
%s actually works for them all, because all Object types have a .toString(), so they can all be converted to Strings for printing.
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