Java泛型理解

 1 　　public static <E> void printArray(E[] inputArray){
 2         for(E elements:inputArray){
 3             System.out.print(elements);
 4         }
 5     }
 6 
 7     public static void main(String[] args){
 8         Integer[] intArray={4,5,6,5,8};
 9         Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };
10         Character[] charArray = { ‘H‘, ‘E‘, ‘L‘, ‘L‘, ‘O‘ };
11 
12         System.out.println( "整型数组元素为:" );
13         printArray( intArray  );
14 
15         System.out.println( "\n双精度型数组元素为:" );
16         printArray( doubleArray );
17 
18         System.out.println( "\n字符型数组元素为:" );
19         printArray( charArray );
20     }

 1 public static <E extends Comparable> E searchMaxnumber(E x,E y,E z){
 2         E maxNumber=x;
 3         if(y.compareTo(maxNumber) > 0){
 4             maxNumber=y;
 5         }
 6         if(z.compareTo(maxNumber)>0){
 7             maxNumber=z;
 8         }
 9         return maxNumber;
10     }
11 
12     public static void main(String[] args){
13         System.out.printf( "%d, %d 和 %d 中最大的数为 %d\n\n",
14                 3, 4, 5, searchMaxnumber( 3, 4, 5 ) );
15         System.out.printf( "%.1f, %.1f 和 %.1f 中最大的数为 %.1f\n\n",
16                 6.6, 8.8, 7.7, searchMaxnumber( 6.6, 8.8, 7.7 ) );
17         System.out.printf( "%s, %s 和 %s 中最大的数为 %s\n","pear",
18                 "apple", "orange", searchMaxnumber( "pear", "apple", "orange" ) );
19     }

 1 public class GenericityExam<E> {
 2 
 3    private E e;
 4 
 5    public E get(){
 6        return e;
 7    }
 8 
 9    public void put(E e){
10        this.e=e;
11    }
12 
13     public static void main(String[] args) {
14         GenericityExam<Integer> integerVal = new GenericityExam<Integer>();
15         GenericityExam<Character> charVal = new GenericityExam<Character>();
16 
17         integerVal.put(new Integer(10));
18         charVal.put(new Character(‘s‘));
19 
20         System.out.printf("整型值为 :%d\n", integerVal.get());
21         System.out.printf("字符为 :%c\n", charVal.get());
22     }
23 
24 }

public static <E> void listGen(List<? extends E> data){
    for(E listData:data){
        System.out.println("data :" + listData);
    }
}

public static void main(String[] args) {
    List<Integer> listIn = new ArrayList<>();
    List<Number> listNu = new ArrayList<>();

    listIn.add(18);
    listIn.add(45);
    listNu.add(314);
    listNu.add(789);

    listGen(listIn);
    listGen(listNu);
}