java - 返回对存储在对象字段之一中的可变对象值的引用会暴露对象的内部表示

Question

在我的代码中为以下几行运行 checkstyle 时出现此错误:

@Override
public String[] getDescriptions() {
    return DESCRIPTIONS;
}

但描述不是可变的。它被定义为:

private static final String[] DESCRIPTIONS = new String[NUM_COLUMNS];

static {
   // In a loop assign values to the array.
   for (int i = 0; i < NUM_COLUMNS; ++i) {
       DESCRIPTIONS[i] = "Some value";
   }
}

这是完整的错误信息:

"Returning a reference to a mutable object value stored in one 
 of the object's fields exposes the internal representation of
 the object. If instances are accessed by untrusted code, and 
 unchecked changes to the mutable object would compromise security
 or other important properties, you will need to do something 
 different. Returning a new copy of the object is better approach
 in many situations."

相关问题:Link

Answer 1

数组和一些集合在其内容仍然可变的意义上并不是不可变的。

Java 中的不变性只涉及对象的引用分配，而不涉及其深层内容。

试试这个:

@Override
public String[] getDescriptions() {
    return Arrays.copyOf(DESCRIPTIONS, DESCRIPTIONS.length);
}

顺便说一句，注意 java 命名约定..:descriptions，而不是 DESCRIPTIONS