菱形

System.out.println("1.第二题");
        System.out.println();
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= m - i; j++) {
                System.out.print(" ");
            }
            
            char charNum1 =  'A';
            int k = 1;
            char strM = 'A';
            for (char str = charNum1; k <= 2 * i - 1; str++) {
                                
                if(k<=i){               
                    System.out.print(str);              
                    strM = str;
                }else{
                    System.out.print(--strM);   
                }
                    
                k++;
                
                    
            }                       
            
            System.out.println();
            Thread.sleep(100);
        }
        
        for (int i = 1; i < m; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(" ");
            }
            char charNum1 =  'A';
            int k = 1;
            char strM = 'A';
            for (char str = charNum1; k <= 2 * (m - i)  - 1; str++) {
                    
                int num = m - i;        
                if(k <  num + 1 ){              
                    System.out.print(str);              
                    strM = str;
                }else{
                    System.out.print(--strM);   
                }
                k++;
            }
            System.out.println();
            Thread.sleep(100);
        }
        System.out.println();