Pad string. (#5669)

java-strings/src/main/java/com/baeldung/string/padding/StringPaddingUtil.java

@@ -0,0 +1,34 @@
+package com.baeldung.string.padding;
+
+public class StringPaddingUtil {
+
+    public static String padLeftSpaces(String inputString, int length) {
+        if (inputString.length() >= length) {
+            return inputString;
+        }
+        StringBuilder sb = new StringBuilder();
+        while (sb.length() < length - inputString.length()) {
+            sb.append(' ');
+        }
+        sb.append(inputString);
+
+        return sb.toString();
+    }
+
+    public static String padLeft(String inputString, int length) {
+        if (inputString.length() >= length) {
+            return inputString;
+        }
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < length; i++) {
+            sb.append(' ');
+        }
+        return sb.substring(inputString.length()) + inputString;
+    }
+
+    public static String padLeftZeros(String inputString, int length) {
+        return String
+          .format("%1$" + length + "s", inputString)
+          .replace(' ', '0');
+    }
+}

java-strings/src/test/java/com/baeldung/string/padding/StringPaddingUtilUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.string.padding;
+
+import com.google.common.base.Strings;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class StringPaddingUtilUnitTest {
+
+    String inputString = "123456";
+    String expectedPaddedStringSpaces = "    123456";
+    String expectedPaddedStringZeros = "0000123456";
+    int minPaddedStringLength = 10;
+
+    @Test
+    public void givenString_whenPaddingWithSpaces_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringSpaces, StringPaddingUtil.padLeftSpaces(inputString, minPaddedStringLength));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithSpacesUsingSubstring_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringSpaces, StringPaddingUtil.padLeft(inputString, minPaddedStringLength));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithZeros_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringZeros, StringPaddingUtil.padLeftZeros(inputString, minPaddedStringLength));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithSpacesUsingStringUtils_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringSpaces, StringUtils.leftPad(inputString, minPaddedStringLength));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithZerosUsingStringUtils_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringZeros, StringUtils.leftPad(inputString, minPaddedStringLength, "0"));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithSpacesUsingGuavaStrings_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringSpaces, Strings.padStart(inputString, minPaddedStringLength, ' '));
+    }
+
+    @Test
+    public void givenString_whenPaddingWithZerosUsingGuavaStrings_thenStringPaddedMatches() {
+        assertEquals(expectedPaddedStringZeros, Strings.padStart(inputString, minPaddedStringLength, '0'));
+    }
+}