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JAVA-25350 Potential issue in "Sorting Java Map in Descending Order" article

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timis1 2023-09-29 09:14:20 +03:00 committed by n
parent 204555a479
commit a50bdf6816
2 changed files with 128 additions and 76 deletions
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76
core-java-modules/core-java-collections-maps-6/src/test/com/baeldung/objecttomap/ObjectToMapUnitTest.java
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@ -1,76 +0,0 @@
package java.com.baeldung.objecttomap;
import com.google.gson.Gson;
import org.junit.Assert;
import org.junit.Test;
import wiremock.com.fasterxml.jackson.core.type.TypeReference;
import wiremock.com.fasterxml.jackson.databind.ObjectMapper;
import wiremock.com.google.common.reflect.TypeToken;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
public class ObjectToMapUnitTest {
Employee employee = new Employee("John", 3000.0);
@Test
public void givenJavaObject_whenUsingReflection_thenConvertToMap() throws IllegalAccessException {
Map<String, Object> map = convertUsingReflection(employee);
Assert.assertEquals(employee.getName(), map.get("name"));
Assert.assertEquals(employee.getSalary(), map.get("salary"));
}
private Map<String, Object> convertUsingReflection(Object object) throws IllegalAccessException {
Map<String, Object> map = new HashMap<>();
Field[] fields = object.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
map.put(field.getName(), field.get(object));
}
return map;
}
@Test
public void givenJavaObject_whenUsingJackson_thenConvertToMap() {
ObjectMapper objectMapper = new ObjectMapper();
Map<String, Object> map = objectMapper.convertValue(employee, new TypeReference<Map<String, Object>>() {});
Assert.assertEquals(employee.getName(), map.get("name"));
Assert.assertEquals(employee.getSalary(), map.get("salary"));
}
@Test
public void givenJavaObject_whenUsingGson_thenConvertToMap() {
Gson gson = new Gson();
String json = gson.toJson(employee);
Map<String, Object> map = gson.fromJson(json, new TypeToken<Map<String, Object>>() {}.getType());
Assert.assertEquals(employee.getName(), map.get("name"));
Assert.assertEquals(employee.getSalary(), map.get("salary"));
}
private static class Employee {
private String name;
private Double salary;
public Employee(String name, Double salary) {
this.name = name;
this.salary = salary;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Double getSalary() {
return salary;
}
public void setSalary(Double age) {
this.salary = salary;
}
}
}

128
core-java-modules/core-java-collections-maps-6/src/test/java/com/baeldung/objecttomap/ObjectToMapUnitTest.java Normal file
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package com.baeldung.objecttomap;
import static org.junit.Assert.assertEquals;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.reflect.TypeToken;
import com.google.gson.Gson;
import org.junit.Test;
import java.lang.reflect.Field;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.stream.Collectors;
public class ObjectToMapUnitTest {
Employee employee = new Employee("John", 3000.0);
@Test
public void givenJavaObject_whenUsingReflection_thenConvertToMap() throws IllegalAccessException {
Map<String, Object> map = convertUsingReflection(employee);
assertEquals(employee.getName(), map.get("name"));
assertEquals(employee.getSalary(), map.get("salary"));
}
private Map<String, Object> convertUsingReflection(Object object) throws IllegalAccessException {
Map<String, Object> map = new HashMap<>();
Field[] fields = object.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
map.put(field.getName(), field.get(object));
}
return map;
}
@Test
public void givenJavaObject_whenUsingJackson_thenConvertToMap() {
ObjectMapper objectMapper = new ObjectMapper();
Map<String, Object> map = objectMapper.convertValue(employee, new TypeReference<Map<String, Object>>() {});
assertEquals(employee.getName(), map.get("name"));
assertEquals(employee.getSalary(), map.get("salary"));
}
@Test
public void givenJavaObject_whenUsingGson_thenConvertToMap() {
Gson gson = new Gson();
String json = gson.toJson(employee);
Map<String, Object> map = gson.fromJson(json, new TypeToken<Map<String, Object>>() {}.getType());
assertEquals(employee.getName(), map.get("name"));
assertEquals(employee.getSalary(), map.get("salary"));
}
@Test
public void given_UnsortedMap_whenSortingByValueDescending_thenValuesAreInDescendingOrder() {
Map<String, Integer> unsortedMap = new HashMap<>();
unsortedMap.put("one", 1);
unsortedMap.put("three", 3);
unsortedMap.put("five", 5);
unsortedMap.put("two", 2);
unsortedMap.put("four", 4);
Map<String, Integer> sortedMap = sortMapByValueDescending(unsortedMap);
assertEquals(5, sortedMap.size());
final Iterator<Integer> iterator = sortedMap.values().iterator();
assertEquals(5, (int) iterator.next());
assertEquals(4, (int) iterator.next());
assertEquals(3, (int) iterator.next());
assertEquals(2, (int) iterator.next());
assertEquals(1, (int) iterator.next());
}
@Test
public void given_UnsortedMap_whenUsingTreeMap_thenKeysAreInDescendingOrder() {
SortedMap<String, Integer> treeMap = new TreeMap<>(Comparator.reverseOrder());
treeMap.put("one", 1);
treeMap.put("three", 3);
treeMap.put("five", 5);
treeMap.put("two", 2);
treeMap.put("four", 4);
assertEquals(5, treeMap.size());
final Iterator<String> iterator = treeMap.keySet().iterator();
assertEquals("two", iterator.next());
assertEquals("three", iterator.next());
assertEquals("one", iterator.next());
assertEquals("four", iterator.next());
assertEquals("five", iterator.next());
}
private static class Employee {
private String name;
private Double salary;
public Employee(String name, Double salary) {
this.name = name;
this.salary = salary;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Double getSalary() {
return salary;
}
public void setSalary(Double age) {
this.salary = salary;
}
}
public static <K, V extends Comparable<? super V>> Map<K, V> sortMapByValueDescending(Map<K, V> map) {
return map.entrySet().stream()
.sorted(Map.Entry.<K, V>comparingByValue().reversed())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e1, LinkedHashMap::new));
}
}