add Concat method (#204)

* feat(strutil): add Concat method

* feat(strutil): add Concat method

strutil/string.go

@@ -617,3 +617,24 @@ func HammingDistance(a, b string) (int, error) {
 
 	return distance, nil
 }
+
+// Concat uses the strings.Builder to concatenate the input strings.
+//   - `length` is the expected length of the concatenated string.
+//   - if you are unsure about the length of the string to be concatenated, please pass 0 or a negative number.
+func Concat(length int, str ...string) string {
+	if len(str) == 0 {
+		return ""
+	}
+
+	sb := strings.Builder{}
+	if length <= 0 {
+		sb.Grow(len(str[0]) * len(str))
+	} else {
+		sb.Grow(length)
+	}
+
+	for _, s := range str {
+		sb.WriteString(s)
+	}
+	return sb.String()
+}

strutil/string_example_test.go

@@ -680,3 +680,17 @@ func ExampleHammingDistance() {
 	// 3
 	// 1
 }
+
+func ExampleConcat() {
+	result1 := Concat(12, "Hello", " ", "World", "!")
+	result2 := Concat(11, "Go", " ", "Language")
+	result3 := Concat(0, "An apple a ", "day，", "keeps the", " doctor away")
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// Hello World!
+	// Go Language
+	// An apple a day，keeps the doctor away
+}

strutil/string_test.go

@@ -561,6 +561,7 @@ func TestContainsAny(t *testing.T) {
 }
 
 func TestRemoveWhiteSpace(t *testing.T) {
+	t.Parallel()
 	assert := internal.NewAssert(t, "TestRemoveWhiteSpace")
 
 	str := " hello   \r\n	\t   world"
@@ -571,6 +572,7 @@ func TestRemoveWhiteSpace(t *testing.T) {
 }
 
 func TestSubInBetween(t *testing.T) {
+	t.Parallel()
 	assert := internal.NewAssert(t, "TestSubInBetween")
 
 	str := "abcde"
@@ -583,6 +585,7 @@ func TestSubInBetween(t *testing.T) {
 }
 
 func TestHammingDistance(t *testing.T) {
+	t.Parallel()
 	assert := internal.NewAssert(t, "HammingDistance")
 
 	hd := func(a, b string) int {
@@ -604,3 +607,16 @@ func TestHammingDistance(t *testing.T) {
 	assert.Equal(0, hd("日本語", "日本語"))
 	assert.Equal(3, hd("日本語", "語日本"))
 }
+
+func TestConcat(t *testing.T) {
+	t.Parallel()
+	assert := internal.NewAssert(t, "TestConcat")
+
+	assert.Equal("", Concat(0))
+	assert.Equal("a", Concat(1, "a"))
+	assert.Equal("ab", Concat(2, "a", "b"))
+	assert.Equal("abc", Concat(3, "a", "b", "c"))
+	assert.Equal("abc", Concat(3, "a", "", "b", "c", ""))
+	assert.Equal("你好，世界！", Concat(0, "你好", "，", "", "世界！", ""))
+	assert.Equal("Hello World!", Concat(0, "Hello", " Wo", "r", "ld!", ""))
+}