[BAEL-11403] - Moved articles out of core-java (part 4)

java-strings/README.md

@@ -45,3 +45,5 @@
 - [Remove or Replace part of a String in Java](https://www.baeldung.com/java-remove-replace-string-part)
 - [Replace a Character at a Specific Index in a String in Java](https://www.baeldung.com/java-replace-character-at-index)
 - [Convert a Comma Separated String to a List in Java](https://www.baeldung.com/java-string-with-separator-to-list)
+- [Guide to java.util.Formatter](http://www.baeldung.com/java-string-formatter)
+- [Add a Character to a String at a Given Position](https://www.baeldung.com/java-add-character-to-string)

java-strings/src/main/java/com/baeldung/string/AppendCharAtPositionX.java

@@ -0,0 +1,45 @@
+/**
+ * 
+ */
+package com.baeldung.string;
+
+/**
+ * @author swpraman
+ *
+ */
+public class AppendCharAtPositionX {
+    
+    public String addCharUsingCharArray(String str, char ch, int position) {
+        validate(str, position);
+        int len = str.length();
+        char[] updatedArr = new char[len + 1];
+        str.getChars(0, position, updatedArr, 0);
+        updatedArr[position] = ch;
+        str.getChars(position, len, updatedArr, position + 1);
+        return new String(updatedArr);
+    }
+
+    public String addCharUsingSubstring(String str, char ch, int position) {
+        validate(str, position);
+        return str.substring(0, position) + ch + str.substring(position);
+    }
+
+    public String addCharUsingStringBuilder(String str, char ch, int position) {
+        validate(str, position);
+        StringBuilder sb = new StringBuilder(str);
+        sb.insert(position, ch);
+        return sb.toString();
+    }
+    
+    private void validate(String str, int position) {
+        if (str == null) {
+            throw new IllegalArgumentException("Str should not be null");
+        }
+        int len = str.length();
+        if (position < 0 || position > len) {
+            throw new IllegalArgumentException("position[" + position + "] should be " 
+                            + "in the range 0.." + len + " for string " + str);
+        }
+    }
+
+}

java-strings/src/test/java/com/baeldung/string/AppendCharAtPositionXUnitTest.java

@@ -0,0 +1,110 @@
+/**
+ * 
+ */
+package com.baeldung.string;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+/**
+ * @author swpraman
+ *
+ */
+public class AppendCharAtPositionXUnitTest {
+    
+    private AppendCharAtPositionX appendCharAtPosition = new AppendCharAtPositionX();
+    private String word = "Titanc";
+    private char letter = 'i';
+    
+    @Test
+    public void whenUsingCharacterArrayAndCharacterAddedAtBeginning_shouldAddCharacter() {
+        assertEquals("iTitanc", appendCharAtPosition.addCharUsingCharArray(word, letter, 0));
+    }
+    
+    @Test
+    public void whenUsingSubstringAndCharacterAddedAtBeginning_shouldAddCharacter() {
+        assertEquals("iTitanc", appendCharAtPosition.addCharUsingSubstring(word, letter, 0));
+    }  
+    
+    @Test
+    public void whenUsingStringBuilderAndCharacterAddedAtBeginning_shouldAddCharacter() {
+        assertEquals("iTitanc", appendCharAtPosition.addCharUsingStringBuilder(word, letter, 0));
+    }
+    
+    @Test
+    public void whenUsingCharacterArrayAndCharacterAddedAtMiddle_shouldAddCharacter() {
+        assertEquals("Titianc", appendCharAtPosition.addCharUsingCharArray(word, letter, 3));
+    }
+    
+    @Test
+    public void whenUsingSubstringAndCharacterAddedAtMiddle_shouldAddCharacter() {
+        assertEquals("Titianc", appendCharAtPosition.addCharUsingSubstring(word, letter, 3));
+    }  
+    
+    @Test
+    public void whenUsingStringBuilderAndCharacterAddedAtMiddle_shouldAddCharacter() {
+        assertEquals("Titianc", appendCharAtPosition.addCharUsingStringBuilder(word, letter, 3));
+    }
+    
+    @Test
+    public void whenUsingCharacterArrayAndCharacterAddedAtEnd_shouldAddCharacter() {
+        assertEquals("Titanci", appendCharAtPosition.addCharUsingCharArray(word, letter, word.length()));
+    }
+    
+    @Test
+    public void whenUsingSubstringAndCharacterAddedAtEnd_shouldAddCharacter() {
+        assertEquals("Titanci", appendCharAtPosition.addCharUsingSubstring(word, letter, word.length()));
+    }  
+    
+    @Test
+    public void whenUsingStringBuilderAndCharacterAddedAtEnd_shouldAddCharacter() {
+        assertEquals("Titanci", appendCharAtPosition.addCharUsingStringBuilder(word, letter, word.length()));
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingCharacterArrayAndCharacterAddedAtNegativePosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, -1);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingSubstringAndCharacterAddedAtNegativePosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, -1);
+    }  
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingStringBuilderAndCharacterAddedAtNegativePosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, -1);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingCharacterArrayAndCharacterAddedAtInvalidPosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, word.length() + 2);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingSubstringAndCharacterAddedAtInvalidPosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, word.length() + 2);
+    }  
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingStringBuilderAndCharacterAddedAtInvalidPosition_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(word, letter, word.length() + 2);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingCharacterArrayAndCharacterAddedAtPositionXAndStringIsNull_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(null, letter, 3);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingSubstringAndCharacterAddedAtPositionXAndStringIsNull_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(null, letter, 3);
+    }  
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void whenUsingStringBuilderAndCharacterAddedAtPositionXAndStringIsNull_shouldThrowException() {
+        appendCharAtPosition.addCharUsingStringBuilder(null, letter, 3);
+    }
+ 
+}

java-strings/src/test/java/com/baeldung/string/formatter/DateToStringFormatterUnitTest.java

@@ -1,7 +1,6 @@
 package com.baeldung.string.formatter;
 
-import org.junit.BeforeClass;
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
 
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
@@ -11,9 +10,11 @@ import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.util.Calendar;
 import java.util.Date;
+import java.util.Locale;
 import java.util.TimeZone;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.BeforeClass;
+import org.junit.Test;
 
 public class DateToStringFormatterUnitTest {
 
@@ -40,7 +41,7 @@ public class DateToStringFormatterUnitTest {
     @Test
     public void whenDateConvertedUsingDateFormatToString_thenCorrect() {
         String formattedDate = DateFormat
-          .getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT)
+          .getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT, Locale.US)
           .format(date);
 
         assertEquals(EXPECTED_STRING_DATE, formattedDate);