com.feilong.core.lang.ObjectUtil Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of feilong Show documentation
Show all versions of feilong Show documentation
feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.
/*
* Copyright (C) 2008 feilong
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.feilong.core.lang;
import static com.feilong.core.Validator.isNotNullOrEmpty;
import com.feilong.core.Validate;
/**
* {@link Object} 工具类.
*
* 判断相等
*
*
*
* - {@link com.feilong.lib.lang3.ObjectUtils#equals(Object, Object)} 支持两个值都是null的情况
* - {@link java.util.Objects#equals(Object, Object)} (since jdk1.7) 也支持两个值都是null的情况
*
*
*
* @author feilong
* @see com.feilong.lib.lang3.ObjectUtils
* @see java.util.Objects
* @since 1.0.0
*/
public final class ObjectUtil{
/** Don't let anyone instantiate this class. */
private ObjectUtil(){
//AssertionError不是必须的. 但它可以避免不小心在类的内部调用构造器. 保证该类在任何情况下都不会被实例化.
//see 《Effective Java》 2nd
throw new AssertionError("No " + getClass().getName() + " instances for you!");
}
//---------------------------------------------------------------
/**
* 如果 object 是null或者empty,返回默认值 defaultValue.
*
* 示例:
*
*
*
*
* ObjectUtil.defaultIfNullOrEmpty(null, null) = null
* ObjectUtil.defaultIfNullOrEmpty(null, "") = ""
* ObjectUtil.defaultIfNullOrEmpty(null, "zz") = "zz"
* ObjectUtil.defaultIfNullOrEmpty("abc", *) = "abc"
* ObjectUtil.defaultIfNullOrEmpty(Boolean.TRUE, *) = Boolean.TRUE
*
*
*
*
* 说明:
*
*
* - 使用该方法,可以简化你的代码
* - 如果使用 import static 的特性,代码会更加简洁
* - 如果你只需要判断 null的场景,你可以使用 {@link #defaultIfNull(Object, Object)}
*
*
*
*
* 对下面的代码重构:
*
*
*
*
*
* if (isNotNullOrEmpty(defaultReturnResult.getReturnObject())){
* return (String) defaultReturnResult.getReturnObject();
* }else{
* return "redirect:/";
* }
*
*
*
* 可以重构成:
*
*
* return ObjectUtil.defaultIfNullOrEmpty((String) defaultReturnResult.getReturnObject(), "redirect:/");
*
*
*
*
* 再比如:
*
*
*
*
*
* private void putItemToMap(Map{@code >} map,String categoryName,Item item){
* List{@code - } itemList = map.get(categoryName);
*
* if (isNullOrEmpty(itemList)){
* itemList = new ArrayList{@code <>}();
* }
* itemList.add(item);
* map.put(categoryName, itemList);
* }
*
*
*
* 可以重构成:
*
*
*
* private void putItemToMap(Map{@code >} map,String categoryName,Item item){
* List{@code - } itemList = ObjectUtil.defaultIfNullOrEmpty(map.get(categoryName), new ArrayList{@code
- }());
* itemList.add(item);
* map.put(categoryName, itemList);
* }
*
*
* 当然对于上面的case,你还可以直接调用 {@link com.feilong.core.util.MapUtil#putMultiValue(java.util.Map, Object, Object)}
*
*
*
* @param
* the type of the object
* @param object
* the {@code Object} to test, 可以是 {@code null} or empty
* @param defaultValue
* the default value to return, 可以是 {@code null} or empty
* @return 如果 object 是null或者empty,返回 defaultValue,否则返回 object
* @see #defaultIfNull(Object, Object)
* @see "org.apache.commons.collections4.ListUtils#defaultIfNull(java.util.List, java.util.List)"
* @since 1.7.2
*/
public static T defaultIfNullOrEmpty(final T object,final T defaultValue){
return isNotNullOrEmpty(object) ? object : defaultValue;
}
/**
* Returns a default value if the object passed is {@code null}.
*
*
* ObjectUtil.defaultIfNull(null, null) = null
* ObjectUtil.defaultIfNull(null, "") = ""
* ObjectUtil.defaultIfNull(null, "zz") = "zz"
* ObjectUtil.defaultIfNull("abc", *) = "abc"
* ObjectUtil.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
*
*
* @param
* the type of the object
* @param object
* the {@code Object} to test, may be {@code null}
* @param defaultValue
* the default value to return, may be {@code null}
* @return {@code object} if it is not {@code null}, defaultValue otherwise
* @since 3.0.0
*/
public static T defaultIfNull(final T object,final T defaultValue){
return object != null ? object : defaultValue;
}
//---------------------------------------------------------------
/**
* 判断指定的对象 object是否是数组.
*
* 说明:
*
*
* - 支持判断原始类型数组
primitive 和包装类型数组
*
*
*
* 示例:
*
*
*
*
* int[] i = {};
* ObjectUtil.isArray(i); =true
*
* ObjectUtil.isArray(new int[] { 1, 2, 3 }); =true
*
* ObjectUtil.isArray(new Integer[0]); =true
* ObjectUtil.isArray(new String[0]); =true
*
*
*
*
* instanceof和 {@link java.lang.Class#isArray()}的区别:
*
*
*
* 通常使用instanceof操作符去判断一个对象 object 是否是数组 array.
* 在JVM层次,instanceof操作符 translates to a specific "instanceof" byte code, which is highly optimized in most JVM
* implementations.
*
*
*
* 而反射的方法(getClass().isArray()) is compiled to two separate "invokevirtual" instructions.
* The more generic optimizations applied by the JVM to these may not be as fast as the hand-tuned optimizations inherent in the
* "instanceof" instruction.
*
*
*
* 有两种特殊情况: null references 和 primitive arrays.
*
*
*
*
*
* instanceofgetClass().isArray()
*
*
* null reference
* false
* NullPointerException
*
*
*
* 原始类型数组primitive array
* false
* true
*
*
*
*
*
* @param object
* the object
* @return 如果 object 是null,抛出 {@link NullPointerException}
* @see Java array reflection: isArray
* vs. instanceof
* @see How to see if
* an object is an array without using reflection?
* @since 1.3.0
*/
public static boolean isArray(Object object){
Validate.notNull(object, "object can't be null!");
return object.getClass().isArray();
}
//---------------------------------------------------------------
/**
* 判断指定的对象 object 是否是原生类型数组.
*
* 示例:
*
*
*
*
*
* ObjectUtil.isPrimitiveArray(1) = false
* ObjectUtil.isPrimitiveArray(1L) = false
* ObjectUtil.isPrimitiveArray("1") = false
*
*
* ObjectUtil.isPrimitiveArray(new int[] {}) = true
* ObjectUtil.isPrimitiveArray(new int[] { 1, 2 }) = true
* ObjectUtil.isPrimitiveArray(new byte[] { 1, 2 }) = true
*
* ObjectUtil.isPrimitiveArray(new String[] { "1", "2" }) = false
*
*
*
*
* @param object
* the object
* @return 如果 object 是null,抛出 {@link NullPointerException}
* @since 1.8.4
*/
public static boolean isPrimitiveArray(Object object){
Validate.notNull(object, "object can't be null!");
return isArray(object) && object.getClass().getComponentType().isPrimitive();//原始型的
}
}