# (DD24) Business Logic — JKKStringUtil.isNullSpace() [8 LOC]

| Field | Value |
|-------|-------|
| Fully Qualified Name | `eo.common.util.JKKStringUtil` |
| Layer | Utility (Common Component) |
| Module | `util` (Package: `eo.common.util`) |

## 1. Role

### JKKStringUtil.isNullSpace()

`isNullSpace()` is a shared utility method that validates whether a given `String` parameter is either `null` or consists solely of whitespace (specifically, half-width/spaces). In business terms, this method serves as a fundamental null-and-blank-check guard that can be applied before any string-based data processing pipeline. It answers the question "does this string field contain no meaningful content?" which is a prerequisite check in many data-validation and input-sanitization flows across the application. The method is implemented as a `static` utility, meaning it is framework-agnostic and callable from any layer without instantiation. It supports no branching by service type or business domain — its single concern is boolean determination of null/whitespace state. The design pattern used is a simple guard check with a negated condition (early return of `true` for invalid input, `false` otherwise). As a shared utility in `eo.common.util`, it plays the role of a cross-cutting validation primitive called by any component that needs to ensure a string carries actual content before proceeding with downstream logic.

## 2. Processing Pattern (Detailed Business Logic)

```mermaid
flowchart TD
    START(["isNullSpace(String str)"])
    COND(["str == null"])
    TRIM(["str.trim()"])
    CMP(["\"\".equals(trimResult)"])
    TRUE_RET(["return true"])
    FALSE_RET(["return false"])
    END_NODE(["Return boolean"])

    START --> COND
    COND -- "true" --> TRUE_RET
    COND -- "false" --> TRIM
    TRIM --> CMP
    CMP -- "true" --> TRUE_RET
    CMP -- "false" --> FALSE_RET
    TRUE_RET --> END_NODE
    FALSE_RET --> END_NODE
```

**Processing Description:**

1. **Entry** — The method receives a `String str` parameter from the caller.
2. **Null Check** — First, it evaluates whether `str` is `null`. If so, the string carries no content at all, so it immediately returns `true` (indicating null/space state).
3. **Whitespace Check** — If `str` is not null, it calls `str.trim()` to remove leading and trailing whitespace characters (including half-width spaces), then compares the result against an empty string `""` using `"\"\".equals(...)"` (null-safe equality check). If the trimmed string is empty, the original string contained only whitespace, so it returns `true`.
4. **Valid String** — If neither condition is met (string is not null and not whitespace-only), the method returns `false`, indicating the string contains meaningful content.

## 3. Parameter Analysis

| No | Parameter Name | Type | Business Description |
|----|---------------|------|---------------------|
| 1 | `str` | `String` | The input string to validate for null or whitespace-only state. Represents any business text field being checked — could be a user-entered value, database column value, API payload field, or internal configuration string. |

**External State:** None. This method is purely functional with no instance fields or external dependencies.

## 4. CRUD Operations / Called Services

This method performs no CRUD operations. It does not call any service components (SC), CBS (Business Service), DAOs, or database access methods.

| CRUD | SC / CBS | SC Code | Entity / DB | Operation Description |
|------|----------|---------|-------------|----------------------|
| — | — | — | — | No CRUD operations. This is a pure utility method. |

**Method Calls Analysis:**

| # | Called Method | Type | Description |
|---|--------------|------|-------------|
| 1 | `String.trim()` | Parameter method | Trims leading/trailing whitespace from the input string |
| 2 | `String.equals(Object)` | Parameter method | Null-safe equality comparison against empty string literal `""` |

## 5. Dependency Trace

No callers were found in the codebase. This method is defined as a `public static` utility but is not actively invoked by any other Java file within the scanned project. It may be used by external modules not included in this codebase, or it may serve as a utility for future development.

| # | Caller (Screen/Batch) | Call Chain (Full Path to this Method) | Terminal (SC / CRUD / Entity) |
|---|----------------------|--------------------------------------|-------------------------------|
| 1 | — | No callers found in this codebase | — |

**Downstream Calls:** This method does not call any other business methods, SC codes, or database operations.

## 6. Per-Branch Detail Blocks

**Block 1** — [IF] `(str == null)` (L53)

> First branch: check if the string reference is null (no object allocated).

| # | Type | Code |
|---|------|------|
| 1 | COND | `str == null` // null-check condition |
| 2 | RETURN | `return true` // [JAVADOC: nullまたは半角スペースの場合、trueを返却] — "If null or half-width space, return true" |

**Block 2** — [IF — OR] `("\"\".equals(str.trim()))"` (L53)

> Second branch: if string is not null, trim whitespace and check if result is empty.

| # | Type | Code |
|---|------|------|
| 1 | EXEC | `str.trim()` // remove leading/trailing whitespace |
| 2 | CALL | `"\"\"".equals(trimResult)` // null-safe equality check against empty string |
| 3 | RETURN | `return true` // [JAVADOC: nullまたは半角スペースの場合、trueを返却] — "If null or half-width space, return true" |

**Block 3** — [ELSE — implicit] `(default return)` (L57)

> Final block: string is neither null nor whitespace-only — valid content exists.

| # | Type | Code |
|---|------|------|
| 1 | RETURN | `return false` // [JAVADOC: false:上記以外] — "false: other than above" |

## 7. Glossary

| Term | Type | Business Meaning |
|------|------|------------------|
| `isNullSpace` | Method | Utility check — determines if a string is null or contains only whitespace |
| `null` | Concept | Java sentinel value indicating no object reference — the string variable holds no value |
| half-width space | Term | ASCII space character (U+0020) as opposed to full-width Japanese space (U+3000); commonly used in Japanese business systems for padding |
| `trim()` | API | Java String method that removes leading and trailing whitespace (spaces, tabs, newlines) from a string |
| `eo.common.util` | Package | Enterprise Operations common utilities package — shared, framework-agnostic helper classes |
| `JKKStringUtil` | Class | String utility helper class containing static methods for common string operations |