BAEL-2392_Java_String_interview_questions second commit (#6064)

java-strings/src/test/java/com/baeldung/string/interview/LocaleUnitTest.java

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+package com.baeldung.string.interview;
+
+import java.math.BigDecimal;
+import java.text.NumberFormat;
+import java.util.Locale;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class LocaleUnitTest {
+    @Test
+    public void whenUsingLocal_thenCorrectResultsForDifferentLocale() {
+        Locale usLocale = Locale.US;
+        BigDecimal number = new BigDecimal(102_300.456d);
+         
+        NumberFormat usNumberFormat = NumberFormat.getCurrencyInstance(usLocale); 
+        assertEquals(usNumberFormat.format(number), "$102,300.46");
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringAnagramUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+
+public class StringAnagramUnitTest {
+    public boolean isAnagram(String s1, String s2) {
+        if(s1.length() != s2.length())
+            return false;
+            
+        char[] arr1 = s1.toCharArray();
+        char[] arr2 = s2.toCharArray();
+        
+        Arrays.sort(arr1);
+        Arrays.sort(arr2);
+        
+        return Arrays.equals(arr1, arr2);
+    }
+    
+    @Test
+    public void whenTestAnagrams_thenTestingCorrectly() {
+        assertThat(isAnagram("car", "arc")).isTrue();
+        assertThat(isAnagram("west", "stew")).isTrue();
+        assertThat(isAnagram("west", "east")).isFalse();
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringChangeCaseUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringChangeCaseUnitTest {
+    @Test
+    public void givenString_whenChangingToUppercase_thenCaseChanged() {
+        String s = "Welcome to Baeldung!";
+        assertEquals("WELCOME TO BAELDUNG!", s.toUpperCase());
+    }
+    
+
+    @Test
+    public void givenString_whenChangingToLowerrcase_thenCaseChanged() {
+        String s = "Welcome to Baeldung!";
+        assertEquals("welcome to baeldung!", s.toLowerCase());
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringCountOccurrencesUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringCountOccurrencesUnitTest {
+    public int countOccurrences(String s, char c) {
+        int count = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == c) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    @Test
+    public void givenString_whenCountingFrequencyOfChar_thenCountCorrect() {
+        assertEquals(3, countOccurrences("united states", 't'));
+    }
+
+    public void givenString_whenUsingJava8_thenCountingOfCharCorrect() {
+        String str = "united states";
+        long count = str.chars().filter(ch -> (char)ch == 't').count();
+        assertEquals(3, count);
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringFormatUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringFormatUnitTest {
+    @Test
+    public void givenString_whenUsingStringFormat_thenStringFormatted() {
+        String title = "Baeldung"; 
+        String formatted = String.format("Title is %s", title);
+        assertEquals(formatted, "Title is Baeldung");
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringInternUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class StringInternUnitTest {
+    @Test
+    public void whenCallingStringIntern_thenStringsInterned() {
+        String s1 = "Baeldung";
+        String s2 = new String("Baeldung");
+        String s3 = new String("Baeldung").intern();
+         
+        assertThat(s1 == s2).isFalse();
+        assertThat(s1 == s3).isTrue();
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringJoinerUnitTest.java

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+package com.baeldung.string.interview;
+
+import java.util.StringJoiner;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringJoinerUnitTest {
+    @Test
+    public void whenUsingStringJoiner_thenStringsJoined() {
+        StringJoiner joiner = new StringJoiner(",", "[", "]");
+        joiner.add("Red")
+          .add("Green")
+          .add("Blue");
+         
+        assertEquals(joiner.toString(), "[Red,Green,Blue]");
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringPalindromeUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class StringPalindromeUnitTest {
+    
+    public boolean isPalindrome(String text) {
+        int forward = 0;
+        int backward = text.length() - 1;
+        while (backward > forward) {
+            char forwardChar = text.charAt(forward++);
+            char backwardChar = text.charAt(backward--);
+            if (forwardChar != backwardChar)
+                return false;
+        }
+        return true;
+    }
+    
+    @Test
+    public void givenIsPalindromeMethod_whenCheckingString_thenFindIfPalindrome() {
+        assertThat(isPalindrome("madam")).isTrue();
+        assertThat(isPalindrome("radar")).isTrue();
+        assertThat(isPalindrome("level")).isTrue();
+
+        assertThat(isPalindrome("baeldung")).isFalse();
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringReverseUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringReverseUnitTest {
+    @Test
+    public void whenUsingInbuildMethods_thenStringReversed() {
+        String reversed = new StringBuilder("baeldung").reverse().toString();
+        assertEquals("gnudleab", reversed);
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringSplitUnitTest.java

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+package com.baeldung.string.interview;
+
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+import static org.junit.Assert.assertArrayEquals;
+
+public class StringSplitUnitTest {
+    @Test
+    public void givenCoreJava_whenSplittingStrings_thenSplitted() {
+        String expected[] = {
+          "john",
+          "peter",
+          "mary"
+        };
+        
+        String[] splitted = "john,peter,mary".split(",");
+        assertArrayEquals( expected, splitted );
+    }
+    
+    @Test
+    public void givenApacheCommons_whenSplittingStrings_thenSplitted() {
+        String expected[] = {
+          "john",
+          "peter",
+          "mary"
+        };
+        String[] splitted = StringUtils.split("john peter mary");
+        assertArrayEquals( expected, splitted );
+    }
+    
+    
+}

java-strings/src/test/java/com/baeldung/string/interview/StringToByteArrayUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertArrayEquals;
+
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
+
+import org.junit.Test;
+
+public class StringToByteArrayUnitTest {
+    @Test
+    public void whenGetBytes_thenCorrect() throws UnsupportedEncodingException {
+        byte[] byteArray1 = "abcd".getBytes();
+        byte[] byteArray2 = "efgh".getBytes(StandardCharsets.US_ASCII);
+        byte[] byteArray3 = "ijkl".getBytes("UTF-8");
+        byte[] expected1 = new byte[] { 97, 98, 99, 100 };
+        byte[] expected2 = new byte[] { 101, 102, 103, 104 };
+        byte[] expected3 = new byte[] { 105, 106, 107, 108 };
+         
+        assertArrayEquals(expected1, byteArray1);
+        assertArrayEquals(expected2, byteArray2);
+        assertArrayEquals(expected3, byteArray3);
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringToCharArrayUnitTest.java

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+package com.baeldung.string.interview;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+
+public class StringToCharArrayUnitTest {
+    @Test
+    public void whenConvertingStringToCharArray_thenConversionSuccessful() {
+        String beforeConvStr = "hello";
+        char[] afterConvCharArr = { 'h', 'e', 'l', 'l', 'o' };
+      
+        assertEquals(Arrays.equals(beforeConvStr.toCharArray(), afterConvCharArr), true);
+    }
+}

java-strings/src/test/java/com/baeldung/string/interview/StringToIntegerUnitTest.java

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+package com.baeldung.string.interview;
+
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringToIntegerUnitTest {
+    @Test
+    public void givenString_whenParsingInt_shouldConvertToInt() {
+        String givenString = "42";
+
+        int result = Integer.parseInt(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+}