자바 범 형 방법 정의 및 범 형 유형 추정

    @Test
    public void test3(){
        //                 
        int x1 = add(3,4);
        Number x2 = add(3.5,4);
        Object obj = add(3,"abc");
    }
    //        <T>
    public <T> T add(T x,T y){
        return x;
    }

    @Test
    public void test4(){
        String[] result = swap(new String[]{"abc","xyz","999"}, 1, 2);
        for(String s:result){
            System.out.println(s);
        }
        Book[] bs = swap(new Book[]{new Book("    ","   "),new Book("   ","   "),new Book("   ","   ")}, 0, 2);
        for(Book b:bs){
            System.out.println(b.getName()+","+b.getAuthor());
        }
        //      ,T        
        //int[] arr = swap(new int[]{1,2,3},1,2);
    }
    //        <T>
    public <T> T[] swap(T[] a,int i,int j){
        T temp = a[i];
        a[i] = a[j];
        a[j] = temp;
        return a;
    }

    @Test
    public void test4(){
        String[] result = swap(new String[]{"abc","xyz","999"}, 1, 2);
        for(String s:result){
            System.out.println(s);
        }
        Book[] bs = swap(new Book[]{new Book("    ","   "),new Book("   ","   "),new Book("   ","   ")}, 0, 2);
        for(Book b:bs){
            System.out.println(b.getName()+","+b.getAuthor());
        }
        //      ,T        
        //int[] arr = swap(new int[]{1,2,3},1,2);
    }
    //        <T>
    public <T extends Object> T[] swap(T[] a,int i,int j){
        T temp = a[i];
        a[i] = a[j];
        a[j] = temp;
        return a;
    }