I want to return valid json string.

Ex:

```json
{
 "status":"Success",
 "total_amt": "41",
 "igst_amt": 14,
 "sgst_amt": 0,
 "cgst_amt": "12",
 "cess_amt": 15
}

```

Expected:

```
{
 "status":"Success",
 "total_amt": "41",
 "igst_amt": "14",
 "sgst_amt": "0",
 "cgst_amt": "12",
 "cess_amt": "15"
} 

```

I have wrote below code:

```
public String toString() {
    return "{\"status\":\"" + status + "\",\"total_amt\":\"" + total_amt + "\",\"igst_amt\":\"" + igst_amt
        + "\",\"sgst_amt\":\"" + sgst_amt + "\",\"cgst_amt:\"" + cgst_amt + "\",\"cess_amt\":\"" + cess_amt + "\"}";
}

```

It is not returning valid JSON.