feat: add trim method for string

Author: easepan

src/main/java/org/code4everything/boot/base/StringUtils.java

@@ -0,0 +1,132 @@
+package org.code4everything.boot.base;
+
+import cn.hutool.core.util.StrUtil;
+
+/**
+ * 字符串工具类
+ *
+ * @author pantao
+ * @since 2019/8/21
+ */
+public class StringUtils {
+
+    private StringUtils() {}
+
+    /**
+     * 裁剪字符串
+     *
+     * @param string 原字符串
+     * @param trimChar 需裁剪的字符
+     * @param mode 如果 {@code mode&3==1}，则裁剪尾部，{@code ==2}裁剪首部，{@code ==3}首尾均裁剪
+     *
+     * @return 裁剪后的字符串
+     *
+     * @since 1.1.6
+     */
+    public static String trim(String string, char trimChar, int mode) {
+        int start = 0;
+        int end = string.length();
+        boolean trimStart = (mode & 2) == 2;
+        if (trimStart) {
+            for (; start < end; start++) {
+                if (string.charAt(start) != trimChar) {
+                    break;
+                }
+            }
+        }
+        boolean trimEnd = (mode & 1) == 1;
+        if (trimEnd) {
+            for (; end > start; end--) {
+                if (string.charAt(end - 1) != trimChar) {
+                    break;
+                }
+            }
+        }
+        return string.substring(start, end);
+    }
+
+    /**
+     * 裁剪字符串
+     *
+     * @param string 原字符串
+     * @param trimStr 需裁剪的字符串
+     *
+     * @return 裁剪后的字符串
+     *
+     * @since 1.1.6
+     */
+    public static String trim(String string, String trimStr) {
+        if (StrUtil.isEmpty(trimStr)) {
+            return string;
+        }
+        int start = trimHelper(string, trimStr, 0, string.length(), trimStr.length());
+        int end = trimHelper(string, trimStr, start, string.length(), -trimStr.length());
+        return string.substring(start, end);
+    }
+
+    /**
+     * 裁剪字符串
+     *
+     * @param string 原字符串
+     * @param trimStr 需裁剪的字符串
+     *
+     * @return 裁剪后的字符串
+     *
+     * @since 1.1.6
+     */
+    public static String trimStart(String string, String trimStr) {
+        if (StrUtil.isEmpty(trimStr)) {
+            return string;
+        }
+        return string.substring(trimHelper(string, trimStr, 0, string.length(), trimStr.length()));
+    }
+
+    /**
+     * 裁剪字符串
+     *
+     * @param string 原字符串
+     * @param trimStr 需裁剪的字符串
+     *
+     * @return 裁剪后的字符串
+     *
+     * @since 1.1.6
+     */
+    public static String trimEnd(String string, String trimStr) {
+        if (StrUtil.isEmpty(trimStr)) {
+            return string;
+        }
+        return string.substring(0, trimHelper(string, trimStr, 0, string.length(), -trimStr.length()));
+    }
+
+    private static int trimHelper(String str, String trim, int start, int end, int step) {
+        if (step == 0) {
+            throw new IllegalArgumentException("step must not be zero");
+        }
+        if (step > 0) {
+            // 裁剪前面
+            if (shouldTrim(str, start, end, trim)) {
+                return trimHelper(str, trim, start + step, end, step);
+            }
+            return start;
+        } else {
+            // 裁剪后面
+            int newEnd = end + step;
+            if (shouldTrim(str, Math.max(start, newEnd), end, trim)) {
+                return trimHelper(str, trim, start, newEnd, step);
+            }
+            return end;
+        }
+    }
+
+    private static boolean shouldTrim(String str, int start, int end, String trim) {
+        if (end - start < trim.length()) {
+            return false;
+        }
+        for (int i = 0; i < trim.length(); i++, start++) {
+            if (str.charAt(start) != trim.charAt(i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

src/test/java/org/code4everything/boot/base/StringUtilsTest.java

@@ -0,0 +1,31 @@
+package org.code4everything.boot.base;
+
+import org.junit.Test;
+
+public class StringUtilsTest {
+
+    @Test
+    public void trim() {
+        assert " b c dda".equals(StringUtils.trim("aa b c dda", "aa"));
+        assert "".equals(StringUtils.trim("abcabcabcabc", "abc"));
+    }
+
+    @Test
+    public void trimStart() {
+        assert "kkgh".equals(StringUtils.trimStart("ghghkkgh", "gh"));
+    }
+
+    @Test
+    public void trimEnd() {
+        assert "aab".equals(StringUtils.trimEnd("aabuiuiuiuiui", "ui"));
+        assert "".equals(StringUtils.trimEnd("123123123123123", "123"));
+    }
+
+    @Test
+    public void testTrim() {
+        String str = "0001001110011000";
+        assert StringUtils.trim(str, "0").equals(StringUtils.trim(str, '0', 3));
+        assert StringUtils.trimStart(str, "0").equals(StringUtils.trim(str, '0', 2));
+        assert StringUtils.trimEnd(str, "0").equals(StringUtils.trim(str, '0', 1));
+    }
+}