Java Generics 简明教程
Java Generics - Methods
你可以编写一个可以针对不同类型参数调用的单个泛型方法声明。根据传递给泛型方法的参数类型，编译器会分别处理每个方法调用。以下是定义泛型方法的规则：
You can write a single generic method declaration that can be called with arguments of different types. Based on the types of the arguments passed to the generic method, the compiler handles each method call appropriately. Following are the rules to define Generic Methods −
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All generic method declarations have a type parameter section delimited by angle brackets (< and >) that precedes the method’s return type ( < E > in the next example).
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Each type parameter section contains one or more type parameters separated by commas. A type parameter, also known as a type variable, is an identifier that specifies a generic type name.
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The type parameters can be used to declare the return type and act as placeholders for the types of the arguments passed to the generic method, which are known as actual type arguments.
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A generic method’s body is declared like that of any other method. Note that type parameters can represent only reference types, not primitive types (like int, double and char).
Example
以下示例说明了如何使用单个泛型方法打印不同类型的数组 -
Following example illustrates how we can print an array of different type using a single Generic method −
public class GenericMethodTest {
// generic method printArray
public static < E > void printArray( E[] inputArray ) {
// Display array elements
for(E element : inputArray) {
System.out.printf("%s ", element);
}
System.out.println();
}
public static void main(String args[]) {
// Create arrays of Integer, Double and Character
Integer[] intArray = { 1, 2, 3, 4, 5 };
Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };
Character[] charArray = { 'H', 'E', 'L', 'L', 'O' };
System.out.println("Array integerArray contains:");
printArray(intArray); // pass an Integer array
System.out.println("\nArray doubleArray contains:");
printArray(doubleArray); // pass a Double array
System.out.println("\nArray characterArray contains:");
printArray(charArray); // pass a Character array
}
}这会产生以下结果 −
This will produce the following result −