Checking if an array is sorted in java (#7273)

* SortedArrayChecker

* add recursivity method with custom object

* change test names

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/SortedArrayChecker.java

@@ -0,0 +1,71 @@
+package com.baeldung.array;
+
+import com.baeldung.arraycopy.model.Employee;
+
+public class SortedArrayChecker {
+    boolean isSorted(int[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2] > array[length - 1])
+            return false;
+
+        return isSorted(array, length - 1);
+    }
+
+    boolean isSorted(int[] array) {
+        for (int i = 0; i < array.length - 1; i++) {
+            if (array[i] > array[i + 1])
+                return false;
+        }
+
+        return true;
+    }
+
+    boolean isSorted(String[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2].compareTo(array[length - 1]) > 0)
+            return false;
+
+        return isSorted(array, length - 1);
+    }
+
+boolean isSorted(String[] array) {
+    for (int i = 0; i < array.length - 1; ++i) {
+        if (array[i].compareTo(array[i + 1]) > 0)
+            return false;
+    }
+
+    return true;
+}
+
+    boolean isSortedByName(Employee[] array) {
+        for (int i = 0; i < array.length - 1; ++i) {
+            if (array[i].getName().compareTo(array[i + 1].getName()) > 0)
+                return false;
+        }
+
+        return true;
+    }
+
+boolean isSortedByAge(Employee[] array) {
+    for (int i = 0; i < array.length - 1; ++i) {
+        if (array[i].getAge() > (array[i + 1].getAge()))
+            return false;
+    }
+
+    return true;
+}
+
+    boolean isSortedByAge(Employee[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2].getAge() > array[length - 1].getAge())
+            return false;
+
+        return isSortedByAge(array, length - 1);
+    }
+}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/arraycopy/model/Employee.java

@@ -6,6 +6,7 @@ public class Employee implements Serializable {
     private static final long serialVersionUID = -2454619097207585825L;
     private int id;
     private String name;
+    private int age;
 
     public Employee() {
     }
@@ -15,10 +16,24 @@ public class Employee implements Serializable {
         this.name = name;
     }
 
+    public Employee(int id, String name, int age) {
+        this.id = id;
+        this.name = name;
+        this.age = age;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
     public int getId() {
         return id;
     }
 
+    public void setAge(int age) {
+        this.age = age;
+    }
+
     public void setId(int id) {
         this.id = id;
     }

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/SortedArrayCheckerUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.array;
+
+import com.baeldung.arraycopy.model.Employee;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SortedArrayCheckerUnitTest {
+
+    private static final int[] INTEGER_SORTED = {1, 3, 5, 7, 9};
+    private static final int[] INTEGER_NOT_SORTED = {1, 3, 11, 7};
+
+    private static final String[] STRING_SORTED = {"abc", "cde", "fgh"};
+    private static final String[] STRING_NOT_SORTED = {"abc", "fgh", "cde", "ijk"};
+
+    private final Employee[] EMPLOYEES_SORTED_BY_NAME = {
+            new Employee(1, "Carlos", 26),
+            new Employee(2, "Daniel", 31),
+            new Employee(3, "Marta", 27)};
+
+    private final Employee[] EMPLOYEES_NOT_SORTED_BY_NAME = {
+            new Employee(1, "Daniel", 31),
+            new Employee(2, "Carlos", 26),
+            new Employee(3, "Marta", 27)};
+
+    private final Employee[] EMPLOYEES_SORTED_BY_AGE = {
+            new Employee(1, "Carlos", 26),
+            new Employee(2, "Marta", 27),
+            new Employee(3, "Daniel", 31)};
+
+    private final Employee[] EMPLOYEES_NOT_SORTED_BY_AGE = {
+            new Employee(1, "Marta", 27),
+            new Employee(2, "Carlos", 26),
+            new Employee(3, "Daniel", 31)};
+
+    private SortedArrayChecker sortedArrayChecker;
+
+    @Before
+    public void setup() {
+        sortedArrayChecker = new SortedArrayChecker();
+    }
+
+    @Test
+    public void givenIntegerArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSorted(INTEGER_SORTED)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(INTEGER_NOT_SORTED)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSorted(INTEGER_SORTED, INTEGER_SORTED.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(INTEGER_NOT_SORTED, INTEGER_NOT_SORTED.length)).isEqualTo(false);
+    }
+
+    @Test
+    public void givenStringArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSorted(STRING_SORTED)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(STRING_NOT_SORTED)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSorted(STRING_SORTED, STRING_SORTED.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(STRING_NOT_SORTED, STRING_NOT_SORTED.length)).isEqualTo(false);
+    }
+
+    @Test
+    public void givenEmployeeArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_SORTED_BY_NAME)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_NOT_SORTED_BY_NAME)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE, EMPLOYEES_SORTED_BY_AGE.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE, EMPLOYEES_NOT_SORTED_BY_AGE.length)).isEqualTo(false);
+    }
+}