Define an utility class to work with the following features.
1. Get all the primitive types
2. Get all the wrapper types
3. Check whether the given class is a primitive or not
4. Check whether the given class is a wrapper or not
5. Convert given primitive type to wrapper type
6. Convert given wrapper type to the primitive type
Primitive types
Java language supports 8 primitive types of data.
1. boolean
2. char
3. byte
4. short
5. int
6. long
7. float
8. double
Wrapper types
Every primitive type has a correspondent wrapper type in java.
|
Primitive Type |
Wrapper Type |
|
boolean |
Boolean |
|
char |
Character |
|
byte |
Byte |
|
short |
Short |
|
int |
Integer |
|
long |
Long |
|
float |
Float |
|
double |
Double |
Find the below working application.
PrimitiveUtil.java
package com.sample.app.util;
import static java.util.Objects.requireNonNull;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class PrimitiveUtil {
private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE_MAP;
private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE_MAP;
private PrimitiveUtil() throws InstantiationException {
throw new InstantiationException("Object creation is restricted");
}
static {
Map<Class<?>, Class<?>> primitiveToWrapperMap = new HashMap<>();
Map<Class<?>, Class<?>> wrapperToPrimitiveMap = new HashMap<>();
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, boolean.class, Boolean.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, char.class, Character.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, byte.class, Byte.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, short.class, Short.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, int.class, Integer.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, long.class, Long.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, float.class, Float.class);
populateMaps(primitiveToWrapperMap, wrapperToPrimitiveMap, double.class, Double.class);
PRIMITIVE_TO_WRAPPER_TYPE_MAP = Collections.unmodifiableMap(primitiveToWrapperMap);
WRAPPER_TO_PRIMITIVE_TYPE_MAP = Collections.unmodifiableMap(wrapperToPrimitiveMap);
}
private static void populateMaps(Map<Class<?>, Class<?>> primitiveToWrapperMap,
Map<Class<?>, Class<?>> wrapperToPrimitiveMap, Class<?> primitiveClass, Class<?> wrapperClass) {
primitiveToWrapperMap.put(primitiveClass, wrapperClass);
wrapperToPrimitiveMap.put(wrapperClass, primitiveClass);
}
public static Set<Class<?>> primitiveTypes() {
return PRIMITIVE_TO_WRAPPER_TYPE_MAP.keySet();
}
public static Set<Class<?>> wrapperTypes() {
return WRAPPER_TO_PRIMITIVE_TYPE_MAP.keySet();
}
public static boolean isPrimitiveType(Class<?> type) {
return type.isPrimitive();
}
public static boolean isWrapperType(Class<?> type) {
return WRAPPER_TO_PRIMITIVE_TYPE_MAP.containsKey(requireNonNull(type));
}
@SuppressWarnings("unchecked")
public static <T> Class<T> toWrapperType(Class<T> type) {
Class<T> wrapperType = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE_MAP.get(requireNonNull(type));
return (wrapperType == null) ? type : wrapperType;
}
@SuppressWarnings("unchecked")
public static <T> Class<T> toPrimitiveType(Class<T> type) {
Class<T> primitiveType = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE_MAP.get(requireNonNull(type));
return (primitiveType == null) ? type : primitiveType;
}
}
PrimitiveUtilDemo.java
package com.sample.app;
import com.sample.app.util.PrimitiveUtil;
public class PrimitiveUtilDemo {
public static void main(String[] args) {
// 1. Get all the primitive types
System.out.println("Primitive types");
PrimitiveUtil.primitiveTypes().forEach(System.out::println);
// 2. Get all the wrapper types
System.out.println("\nWrapper types");
PrimitiveUtil.wrapperTypes().forEach(System.out::println);
// 3. Check whether the given class is a primitive or not
System.out.println("\nIs " + long.class + " primitive ? " + PrimitiveUtil.isPrimitiveType(long.class));
System.out.println("Is " + Long.class + " primitive ? " + PrimitiveUtil.isPrimitiveType(Long.class));
// 4. Check whether the given class is a wrapper or not
System.out.println("\nIs " + long.class + " wrapper ? " + PrimitiveUtil.isWrapperType(long.class));
System.out.println("Is " + Long.class + " wrapper ? " + PrimitiveUtil.isWrapperType(Long.class));
// 5. Convert given primitive type to wrapper type
System.out.println("\ntoWrapperType(long.class) : " + PrimitiveUtil.toWrapperType(long.class));
// 6. Convert given wrapper type to the primitive type
System.out.println("\ntoPrimitiveType(Long.class) : " + PrimitiveUtil.toPrimitiveType(Long.class));
}
}
Output
Primitive types int short long boolean float byte double char Wrapper types class java.lang.Byte class java.lang.Short class java.lang.Integer class java.lang.Long class java.lang.Double class java.lang.Character class java.lang.Float class java.lang.Boolean Is long primitive ? true Is class java.lang.Long primitive ? false Is long wrapper ? false Is class java.lang.Long wrapper ? true toWrapperType(long.class) : class java.lang.Long toPrimitiveType(Long.class) : long
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