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  • Hbase delete遇到的常见异常: Exception in thread "main" java.lang.UnsupportedOperationException

    hbase 执行批量删除时出现错误:
     Exception in thread "main" java.lang.UnsupportedOperationException
    at java.util.AbstractList.remove(AbstractList.java:161)
    at org.apache.hadoop.hbase.client.HTable.delete(HTable.java:852)

    这种异常其实很常见,remove操作不支持,为什么会出现不支持的情况呢?检查代码时发现传参list 是通过Arrays.asList()创建的,

    很明显,问题就是这个地方导致的,Arrays.asList()返回是实际上是Arrays类内部的一个实现ArrayList:

       /**
         * @serial include
         */
        private static class ArrayList<E> extends AbstractList<E>
            implements RandomAccess, java.io.Serializable
        {
            private static final long serialVersionUID = -2764017481108945198L;
            private final E[] a;
    
            ArrayList(E[] array) {
                if (array==null)
                    throw new NullPointerException();
                a = array;
            }
    
            public int size() {
                return a.length;
            }
    
            public Object[] toArray() {
                return a.clone();
            }
    
            public <T> T[] toArray(T[] a) {
                int size = size();
                if (a.length < size)
                    return Arrays.copyOf(this.a, size,
                                         (Class<? extends T[]>) a.getClass());
                System.arraycopy(this.a, 0, a, 0, size);
                if (a.length > size)
                    a[size] = null;
                return a;
            }
    
            public E get(int index) {
                return a[index];
            }
    
            public E set(int index, E element) {
                E oldValue = a[index];
                a[index] = element;
                return oldValue;
            }
    
            public int indexOf(Object o) {
                if (o==null) {
                    for (int i=0; i<a.length; i++)
                        if (a[i]==null)
                            return i;
                } else {
                    for (int i=0; i<a.length; i++)
                        if (o.equals(a[i]))
                            return i;
                }
                return -1;
            }
    
            public boolean contains(Object o) {
                return indexOf(o) != -1;
            }
        }

    Arrays.ArrayList继承至AbstractList,AbstractList本身是不支持删除操作的,Arrays.ArrayList也没有重现remove方法,因此,如果通过Arrays.asList()创建的ArrayList,如果调用了remove方法,则会出现UnsupportedOperationException异常。

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  • 原文地址:https://www.cnblogs.com/jessezeng/p/6443253.html
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