Merge pull request #7489 from M-Abdelbaset/public-access-modifier

BAEL-3148

core-java-modules/core-java-lang-oop-2/pom.xml

@@ -14,6 +14,19 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
+	<dependencies>
+		<dependency>
+			<groupId>com.h2database</groupId>
+			<artifactId>h2</artifactId>
+			<version>${h2.version}</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+    <properties>
+        <h2.version>1.4.199</h2.version>
+    </properties>
+    
     <build>
         <finalName>core-java-lang-oop-2</finalName>
         <resources>

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/accessmodifiers/publicmodifier/ListOfThree.java

@@ -0,0 +1,31 @@
+package com.baeldung.accessmodifiers.publicmodifier;
+
+import java.util.AbstractList;
+import java.util.Arrays;
+
+public class ListOfThree<E> extends AbstractList<E> {
+
+    private static final int LENGTH = 3;
+    private Object[] elements;
+    
+    public ListOfThree(E[] data) {
+        if(data == null 
+            || data.length != LENGTH)
+            throw new IllegalArgumentException();
+        
+        this.elements = Arrays.copyOf(data, data.length); //shallow copy
+        
+    }
+    
+    @Override
+    @SuppressWarnings("unchecked")
+    public E get(int index) {      
+        return (E)elements[index];
+    }
+    
+    @Override
+    public int size() {
+        return LENGTH;
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/accessmodifiers/publicmodifier/SpecialCharacters.java

@@ -0,0 +1,7 @@
+package com.baeldung.accessmodifiers.publicmodifier;
+
+public class SpecialCharacters {
+
+    public static final String SLASH = "/";
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/accessmodifiers/publicmodifier/Student.java

@@ -0,0 +1,67 @@
+package com.baeldung.accessmodifiers.publicmodifier;
+
+import java.math.BigDecimal;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.util.Date;
+
+public class Student {
+
+    private StudentGrade grade; //new data representation
+//    private int grade; //old data representation
+    private String name;   
+    private int age;
+    
+    public void setGrade(int grade) {        
+        this.grade = new StudentGrade(grade);
+    }
+
+    public int getGrade() {
+        return this.grade.getGrade().intValue(); //int is returned for backward compatibility
+    }
+    
+    public Connection getConnection() throws SQLException {
+        
+        final String URL = "jdbc:h2:~/test";
+        return DriverManager.getConnection(URL, "sa", "");
+
+    }
+        
+    public void setAge(int age) {
+        if (age < 0 || age > 150) {
+            throw new IllegalArgumentException();
+        }
+        
+        this.age = age;
+    }
+
+    public int getAge() {
+        return age;
+    }
+    
+    @Override
+    public String toString() {
+        return this.name;
+    }
+
+    private class StudentGrade {
+        private BigDecimal grade = BigDecimal.ZERO;
+        private Date updatedAt;
+        
+        public StudentGrade(int grade) {
+            this.grade = new BigDecimal(grade);
+            this.updatedAt = new Date();
+        }
+        
+        public BigDecimal getGrade() {
+            return grade;
+        }
+        
+        public Date getDate() {
+            return updatedAt;
+        }
+        
+     }
+    
+}

core-java-modules/core-java-lang-oop-2/src/test/java/com/baeldung/accessmodifiers/PublicAccessModifierUnitTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.accessmodifiers;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.TestInstance.Lifecycle;
+import com.baeldung.accessmodifiers.publicmodifier.ListOfThree;
+import com.baeldung.accessmodifiers.publicmodifier.Student;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import java.math.BigDecimal;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@TestInstance(Lifecycle.PER_CLASS)
+public class PublicAccessModifierUnitTest {
+
+    @Test
+    public void whenUsingBigDecimalIntValueMethod_correspondingIntIsReturned() {
+        assertEquals(0, new BigDecimal(0).intValue()); //instance member
+    }
+    
+    @Test
+    public void whenUsingIntegerMaxValueField_maxPossibleIntValueIsReturned() {
+        assertEquals(2147483647, Integer.MAX_VALUE); //static field
+    }
+    
+    @Test
+    public void whenChangingStudentInternalRepresentation_clientCodeWillNotBreak() {
+        
+        Student student = new Student();
+        student.setGrade(100);
+        
+        assertEquals(100, student.getGrade());
+    }
+    
+    @Test
+    public void whenUsingEntrySet_keyValuePairsAreReturned() {
+        
+        Map<String, String> mapObject = new HashMap<String, String>();
+        mapObject.put("name", "Alex");
+       
+        for(Map.Entry<String, String> entry : mapObject.entrySet()) {
+            assertEquals("name", entry.getKey());
+            assertEquals("Alex", entry.getValue());
+        }
+        
+    }
+    
+    @Test
+    public void whenUsingStringToLowerCase_stringTurnsToLowerCase() {
+        assertEquals("alex", "ALEX".toLowerCase());
+    }
+
+    @Test
+    public void whenParsingStringOne_parseIntReturns1() {
+        assertEquals(1, Integer.parseInt("1"));
+    }
+    
+    @Test
+    public void whenConnectingToH2_connectionInstanceIsReturned() throws SQLException {
+
+        final String url = "jdbc:h2:~/test";
+        Connection conn = DriverManager.getConnection(url, "sa", "");
+        assertNotNull(conn);
+    }
+
+    @Test
+    public void whenCreatingCustomList_concreteAndInheritedMethodsWork() {
+
+        String[] dataSet1 = new String[] {"zero", "one", "two"};
+        
+        List<String> list1 = new ListOfThree<String>(dataSet1);
+        
+        //our implemented methods
+        assertEquals("one", list1.get(1));
+        assertEquals(3, list1.size());
+
+        //inherited implementations
+        assertEquals(1, list1.indexOf("one"));
+        
+        String[] dataSet2 = new String[] {"two", "zero", "one"};
+        List<String> list2 = new ListOfThree<String>(dataSet2);
+        
+        assertTrue(list1.containsAll(list2));
+    }
+    
+}