java Java比较数组
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Java comparing Arrays
提问by DD.
I have two Arrays of unknown type...is there a way to check the elements are the same:
我有两个未知类型的数组……有没有办法检查元素是否相同：
public static boolean equals(Object a , Object b) {
if (a instanceof int[])
return Arrays.equals((int[]) a, (int[])b);
if (a instanceof double[]){
////etc
}
I want to do this without all the instanceof checks....
我想在没有所有 instanceof 检查的情况下执行此操作....
回答by Tomasz Nurkiewicz
ArrayUtils.isEquals()from Apache Commonsdoes exactly that. It also handles multi-dimensional arrays.
来自Apache Commons 的ArrayUtils.isEquals()正是这样做的。它还处理多维数组。
回答by Eng.Fouad
You should try Arrays.deepEquals(a, b)
你应该试试 Arrays.deepEquals(a, b)
回答by Miquel
Arrays utilities class could be of help for this:
Arrays 实用程序类可能对此有所帮助：
http://download.oracle.com/javase/1.4.2/docs/api/java/util/Arrays.html
http://download.oracle.com/javase/1.4.2/docs/api/java/util/Arrays.html
There is a method:
有一个方法：
equals(Object[] a, Object[] a2)
That compares arrays of objects.
比较对象数组。
回答by Peter Walser
If the array type is unknown, you cannot simply cast to Object[], and therefore cannot use the methods (equals, deepEquals) in java.util.Arrays.
You can however use reflection to get the length and items of the arrays, and compare them recursively (the items may be arrays themselves).
如果数组类型未知，则不能简单地强制转换为Object[]，因此不能使用 中的方法 ( equals, deepEquals) java.util.Arrays。
但是，您可以使用反射来获取数组的长度和项目，并递归地比较它们（项目本身可能是数组）。
Here's a general utility method to compare two objects(arrays are also supported), which allows one or even both to be null:
这是比较两个对象（也支持数组）的通用实用方法，它允许一个或什至两个对象为空：
public static boolean equals (Object a, Object b) {
if (a == b) {
return true;
}
if (a == null || b == null) {
return false;
}
if (a.getClass().isArray() && b.getClass().isArray()) {
int length = Array.getLength(a);
if (length > 0 && !a.getClass().getComponentType().equals(b.getClass().getComponentType())) {
return false;
}
if (Array.getLength(b) != length) {
return false;
}
for (int i = 0; i < length; i++) {
if (!equals(Array.get(a, i), Array.get(b, i))) {
return false;
}
}
return true;
}
return a.equals(b);
}
