Spring util工具类ObjectUtils源码

package org.springframework.util;

import java.lang.reflect.Array;
import java.util.Arrays;

/**
*该工具类采用抽象类定义，抽象类内部全采用静态方法
*通常情况下定义工具类有如下方法：
*Method I:定义final类，私有化构造函数，类内部全采用静态方法
*Method II:定义abstract类，类内部全采用静态方法
*Method III:不建议采用接口+静态方法 或者 非私有化构造函数+静态方法
 */
public abstract class ObjectUtils {
    /** 初始Hash*/
    private static final int INITIAL_HASH = 7;
    /** Hash乘数*/
    private static final int MULTIPLIER = 31;

    /** 逻辑空串*/
    private static final String EMPTY_STRING = "";
    /** 实际空串*/
    private static final String NULL_STRING = "null";
    /** 数组开始*/
    private static final String ARRAY_START = "{";
    /** 数组结尾*/
    private static final String ARRAY_END = "}";
    private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END;
    /** 数组分隔符*/
    private static final String ARRAY_ELEMENT_SEPARATOR = ", ";


    //判断对象是否为可检查异常，即是RuntimeException或Error的实例
    public static boolean isCheckedException(Throwable ex) {
        return !(ex instanceof RuntimeException || ex instanceof Error);
    }

    //是否可兼容异常，即是继承自RuntimeException和Error的异常或者自定义的declaredExceptions的实例
    public static boolean isCompatibleWithThrowsClause(Throwable ex, Class<?>... declaredExceptions) {
        if (!isCheckedException(ex)) {
            return true;
        }
        if (declaredExceptions != null) {
            for (Class<?> declaredException : declaredExceptions) {
                if (declaredException.isInstance(ex)) {
                    return true;
                }
            }
        }
        return false;
    }

    //判断对象是否为数组obj.getClass().isArray()
    public static boolean isArray(Object obj) {
        return (obj != null && obj.getClass().isArray());
    }

    //判断数组为空
    public static boolean isEmpty(Object[] array) {
        return (array == null || array.length == 0);
    }

    //判断数组包含元素
    public static boolean containsElement(Object[] array, Object element) {
        if (array == null) {
            return false;
        }
        for (Object arrayEle : array) {
            //非空安全相等，即在同为空值时默认不相等
            if (nullSafeEquals(arrayEle, element)) {
                return true;
            }
        }
        return false;
    }

    //包含常量，对枚举类型有效
    public static boolean containsConstant(Enum<?>[] enumValues, String constant) {
        return containsConstant(enumValues, constant, false);
    }

    //包含常量，对枚举类型有效，大小写敏感
    public static boolean containsConstant(Enum<?>[] enumValues, String constant, boolean caseSensitive) {
        for (Enum<?> candidate : enumValues) {
            if (caseSensitive ?
                    candidate.toString().equals(constant) :
                    candidate.toString().equalsIgnoreCase(constant)) {
                return true;
            }
        }
        return false;
    }

    //枚举类型的大小写不敏感valueOf()
    public static <E extends Enum<?>> E caseInsensitiveValueOf(E[] enumValues, String constant) {
        for (E candidate : enumValues) {
            if(candidate.toString().equalsIgnoreCase(constant)) {
                return candidate;
            }
        }
        throw new IllegalArgumentException(
                String.format("constant [%s] does not exist in enum type %s",
                        constant, enumValues.getClass().getComponentType().getName()));
    }

    //数组添加元素，被添加的元素必须是A元素的子类以保证数组元素类型的一致性
    public static <A, O extends A> A[] addObjectToArray(A[] array, O obj) {
        //首先默认为最顶级的Object类型，如果array不空采用A，否则如果obj不空采用O，否则就是默认的Object类型
        Class<?> compType = Object.class;
        if (array != null) {
            compType = array.getClass().getComponentType();
        }
        else if (obj != null) {
            compType = obj.getClass();
        }
        int newArrLength = (array != null ? array.length + 1 : 1);
        @SuppressWarnings("unchecked")
        //调用Array工具类的newInstance来创建数组对象
        A[] newArr = (A[]) Array.newInstance(compType, newArrLength);
        if (array != null) {
            System.arraycopy(array, 0, newArr, 0, array.length);
        }
        newArr[newArr.length - 1] = obj;
        return newArr;
    }

    //转为Object数组，不管是什么类型的数组统统转为Object数组的表达方式
    public static Object[] toObjectArray(Object source) {
        if (source instanceof Object[]) {
            return (Object[]) source;
        }
        if (source == null) {
            return new Object[0];
        }
        if (!source.getClass().isArray()) {
            throw new IllegalArgumentException("Source is not an array: " + source);
        }
        int length = Array.getLength(source);
        if (length == 0) {
            return new Object[0];
        }
        Class<?> wrapperType = Array.get(source, 0).getClass();
        Object[] newArray = (Object[]) Array.newInstance(wrapperType, length);
        for (int i = 0; i < length; i++) {
            newArray[i] = Array.get(source, i);
        }
        return newArray;
    }


    //直接调用Arrays.equals()来判断基本数据类型数组，其他的调用equals()来比较，具体的取决于equals()的实现
    public static boolean nullSafeEquals(Object o1, Object o2) {
        if (o1 == o2) {
            return true;
        }
        if (o1 == null || o2 == null) {
            return false;
        }
        if (o1.equals(o2)) {
            return true;
        }
        if (o1.getClass().isArray() && o2.getClass().isArray()) {
            if (o1 instanceof Object[] && o2 instanceof Object[]) {
                return Arrays.equals((Object[]) o1, (Object[]) o2);
            }
            if (o1 instanceof boolean[] && o2 instanceof boolean[]) {
                return Arrays.equals((boolean[]) o1, (boolean[]) o2);
            }
            if (o1 instanceof byte[] && o2 instanceof byte[]) {
                return Arrays.equals((byte[]) o1, (byte[]) o2);
            }
            if (o1 instanceof char[] && o2 instanceof char[]) {
                return Arrays.equals((char[]) o1, (char[]) o2);
            }
            if (o1 instanceof double[] && o2 instanceof double[]) {
                return Arrays.equals((double[]) o1, (double[]) o2);
            }
            if (o1 instanceof float[] && o2 instanceof float[]) {
                return Arrays.equals((float[]) o1, (float[]) o2);
            }
            if (o1 instanceof int[] && o2 instanceof int[]) {
                return Arrays.equals((int[]) o1, (int[]) o2);
            }
            if (o1 instanceof long[] && o2 instanceof long[]) {
                return Arrays.equals((long[]) o1, (long[]) o2);
            }
            if (o1 instanceof short[] && o2 instanceof short[]) {
                return Arrays.equals((short[]) o1, (short[]) o2);
            }
        }
        return false;
    }

    //求得hashCode，当值为null时，hashCode为0
    public static int nullSafeHashCode(Object obj) {
        if (obj == null) {
            return 0;
        }
        if (obj.getClass().isArray()) {
            if (obj instanceof Object[]) {
                return nullSafeHashCode((Object[]) obj);
            }
            if (obj instanceof boolean[]) {
                return nullSafeHashCode((boolean[]) obj);
            }
            if (obj instanceof byte[]) {
                return nullSafeHashCode((byte[]) obj);
            }
            if (obj instanceof char[]) {
                return nullSafeHashCode((char[]) obj);
            }
            if (obj instanceof double[]) {
                return nullSafeHashCode((double[]) obj);
            }
            if (obj instanceof float[]) {
                return nullSafeHashCode((float[]) obj);
            }
            if (obj instanceof int[]) {
                return nullSafeHashCode((int[]) obj);
            }
            if (obj instanceof long[]) {
                return nullSafeHashCode((long[]) obj);
            }
            if (obj instanceof short[]) {
                return nullSafeHashCode((short[]) obj);
            }
        }
        return obj.hashCode();
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(Object[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (Object element : array) {
            hash = MULTIPLIER * hash + nullSafeHashCode(element);
        }
        return hash;
    }
    
    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(boolean[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (boolean element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(byte[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (byte element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(char[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (char element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(double[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (double element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(float[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (float element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(int[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (int element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(long[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (long element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }
    
    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(short[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (short element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    //boolean值就两个hash值，1231和1237
    public static int hashCode(boolean bool) {
        return (bool ? 1231 : 1237);
    }

    
    /**
    直接调用Double.hashCode(value);
     long bits = doubleToLongBits(value);
      return (int)(bits ^ (bits >>> 32));
    */
    public static int hashCode(double dbl) {
        return hashCode(Double.doubleToLongBits(dbl));
    }

    //同上
    public static int hashCode(float flt) {
        return Float.floatToIntBits(flt);
    }

    //同上
    public static int hashCode(long lng) {
        return (int) (lng ^ (lng >>> 32));
    }

    //object转字符串，基本上等同于obj.toString(),唯一不同的是空对象仍然有效
    //与String.valueOf(obj)也类似，但是空对象是“”而不是"null"
    public static String identityToString(Object obj) {
        if (obj == null) {
            return EMPTY_STRING;
        }
        return obj.getClass().getName() + "@" + getIdentityHexString(obj);
    }

    
    public static String getIdentityHexString(Object obj) {
        return Integer.toHexString(System.identityHashCode(obj));
    }

    //转成显示的字符串，将数组显示出来
    public static String getDisplayString(Object obj) {
        if (obj == null) {
            return EMPTY_STRING;
        }
        return nullSafeToString(obj);
    }

    
    public static String nullSafeClassName(Object obj) {
        return (obj != null ? obj.getClass().getName() : NULL_STRING);
    }

    //对数组进行了处理，其余的类似String.valueOf(obj)
    public static String nullSafeToString(Object obj) {
        if (obj == null) {
            return NULL_STRING;
        }
        if (obj instanceof String) {
            return (String) obj;
        }
        if (obj instanceof Object[]) {
            return nullSafeToString((Object[]) obj);
        }
        if (obj instanceof boolean[]) {
            return nullSafeToString((boolean[]) obj);
        }
        if (obj instanceof byte[]) {
            return nullSafeToString((byte[]) obj);
        }
        if (obj instanceof char[]) {
            return nullSafeToString((char[]) obj);
        }
        if (obj instanceof double[]) {
            return nullSafeToString((double[]) obj);
        }
        if (obj instanceof float[]) {
            return nullSafeToString((float[]) obj);
        }
        if (obj instanceof int[]) {
            return nullSafeToString((int[]) obj);
        }
        if (obj instanceof long[]) {
            return nullSafeToString((long[]) obj);
        }
        if (obj instanceof short[]) {
            return nullSafeToString((short[]) obj);
        }
        String str = obj.toString();
        return (str != null ? str : EMPTY_STRING);
    }

    
    public static String nullSafeToString(Object[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(String.valueOf(array[i]));
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(boolean[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(byte[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(char[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append("'").append(array[i]).append("'");
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(double[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(float[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(int[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(long[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(short[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

}