[regex-squre-brackets] Extract Text Between Square Brackets (#14635)

core-java-modules/core-java-regex-2/src/test/java/com/baeldung/regex/squarebrackets/ExtractTextBetweenSquareBracketsUnitTest.java

@@ -0,0 +1,98 @@
+package com.baeldung.regex.squarebrackets;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.junit.jupiter.api.Test;
+
+import com.google.common.collect.Lists;
+
+public class ExtractTextBetweenSquareBracketsUnitTest {
+    static final String INPUT1 = "some text [THE IMPORTANT MESSAGE] something else";
+    static final String EXPECTED1 = "THE IMPORTANT MESSAGE";
+
+    static final String INPUT2 = "[La La Land], [The last Emperor], and [Life of Pi] are all great movies.";
+    static final List<String> EXPECTED2 = Lists.newArrayList("La La Land", "The last Emperor", "Life of Pi");
+
+    @Test
+    void whenUsingDotStarOnInput1_thenGetExpectedResult() {
+        String result = null;
+        String rePattern = "\\[(.*)]";
+        Pattern p = Pattern.compile(rePattern);
+        Matcher m = p.matcher(INPUT1);
+        if (m.find()) {
+            result = m.group(1);
+        }
+        assertThat(result).isEqualTo(EXPECTED1);
+    }
+
+    @Test
+    void whenUsingCharClassOnInput1_thenGetExpectedResult() {
+        String result = null;
+        String rePattern = "\\[([^]]*)";
+        Pattern p = Pattern.compile(rePattern);
+        Matcher m = p.matcher(INPUT1);
+        if (m.find()) {
+            result = m.group(1);
+        }
+        assertThat(result).isEqualTo(EXPECTED1);
+    }
+
+    @Test
+    void whenUsingSplitOnInput1_thenGetExpectedResult() {
+        String[] strArray = INPUT1.split("[\\[\\]]", -1);
+        String result = strArray.length == 3 ? strArray[1] : null;
+
+        assertThat(result).isEqualTo(EXPECTED1);
+    }
+
+    @Test
+    void whenUsingSplitWithLimit_thenGetExpectedResult() {
+        String[] strArray = "[THE IMPORTANT MESSAGE]".split("[\\[\\]]");
+        assertThat(strArray).hasSize(2)
+          .containsExactly("", "THE IMPORTANT MESSAGE");
+
+        strArray = "[THE IMPORTANT MESSAGE]".split("[\\[\\]]", -1);
+        assertThat(strArray).hasSize(3)
+          .containsExactly("", "THE IMPORTANT MESSAGE", "");
+    }
+
+    @Test
+    void whenUsingNonGreedyOnInput2_thenGetExpectedResult() {
+        List<String> result = new ArrayList<>();
+        String rePattern = "\\[(.*?)]";
+        Pattern p = Pattern.compile(rePattern);
+        Matcher m = p.matcher(INPUT2);
+        while (m.find()) {
+            result.add(m.group(1));
+        }
+        assertThat(result).isEqualTo(EXPECTED2);
+    }
+
+    @Test
+    void whenUsingCharClassOnInput2_thenGetExpectedResult() {
+        List<String> result = new ArrayList<>();
+        String rePattern = "\\[([^]]*)";
+        Pattern p = Pattern.compile(rePattern);
+        Matcher m = p.matcher(INPUT2);
+        while (m.find()) {
+            result.add(m.group(1));
+        }
+        assertThat(result).isEqualTo(EXPECTED2);
+    }
+
+    @Test
+    void whenUsingSplitInput2_thenGetExpectedResult() {
+        List<String> result = new ArrayList<>();
+        String[] strArray = INPUT2.split("[\\[\\]]", -1);
+        for (int i = 1; i < strArray.length; i += 2) {
+            result.add(strArray[i]);
+        }
+        assertThat(result).isEqualTo(EXPECTED2);
+    }
+
+}