问Scanner.nextLine()抛出java.util.InputMismatchException

EN

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:864)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at inventory.items.Inventory.add(Inventory.java:24)
at inventory.items.Inventory.main(Inventory.java:98)

public class Inventory extends Item implements Actions{
int num1, num2;
String S1;
Item a = new Item();
Item b = new Item();   
Scanner Sc = new Scanner(System.in);
@Override
public void add() {

System.out.println("Please enter the new item specifications as follows: 1. Quantity  2. Name  3. Price");

 num1 = Sc.nextInt();

 a.setQuantity(num1);

 S1 = Sc.nextLine();

 a.setName(S1);

 num2 = Sc.nextInt();

 a.setPrice(num2);

}

/**
 *
 * @param b
 */
@Override
public void remove(Item b) {
b = null;
System.gc();   
}

/**
 *
 * @param E
 */
@Override
public void edit(String E) {
E = Sc.nextLine();

if(a.getName().equals(b)){
System.out.println("Please edit the item specifications as follows: 1. Quantity  2. Name  3. Price ");

 num1 = Sc.nextInt();

 S1 = Sc.nextLine();

 num2 = Sc.nextInt();

 a.setQuantity(num1);

 a.setName(S1);

 a.setPrice(num2);   
 }
 else{
 System.out.println("You can't edit a non existent item. The items are case 
 sensitive.");    
 }
 }

 /**
 *
 * @param Info
 */
 @Override
 public void info(String Info) {
 if(a.getName().equals(Info)){    
 System.out.println("Item name : " + a.getName() + " Item price: " + 
 a.getPrice() + " Item Quantity: "  + a.getQuantity());
 }
 else{
 System.out.println("Please enter a an existing item name!");        
 }

 }
 public static void main (String [] args){
 Inventory inv = new Inventory();

 Scanner Sc1 = new Scanner(System.in);

 Item a = new Item();
 Item b = new Item();   

 String I = "";

 System.out.println("Please enter one of the following commands: 1. add   2. 
 edit   3. remove    4. info ");

  I = Sc1.nextLine();

 switch (I){
case "add" :
  inv.add();
  break;
case "edit" :
  System.out.println("Enter the name of the item you want to edit: ");
  String Input2 = Sc1.nextLine();
  inv.edit(Input2);
  break;
case "remove" :
  System.out.println("Enter the name of the item you want to remove: ");
  inv.remove(a);
  break;
case "info" :
  System.out.println("Enter the name of the item you want too see its info.");
  String Inf = Sc1.nextLine();
  inv.info(Inf);
default : 
  System.out.println("Please enter a valid command! The commands ARE case- 
  sensitive.");
}
}   
}

class Item{

private int q,p;
private String n;

private int quantity =  0;
private String name = " ";
private int price = 0;

public void setQuantity(int q){
this.quantity = q;
}
public int getQuantity(){
return q;
}

public void setName(String n){
this.name = n;
}
public String getName(){
return n;
}
public void setPrice(int p){
this.price = p;
}
public int getPrice(){
return p;
}
}

interface Actions {
void add();
void remove(Item b);
void edit(String E);
void info(String Info);
}