Java substring 遇到的坑

旧城等待， 2021-12-10 06:23 314阅读 0赞

如下：定义一个string【长度为6，那么下标就应该是0到5】：

String s = "123456";

我们如何取出整个s呢？  
当初我的想法是s.substring(0,5);======>>>>试验一下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwOTY5MTA4_size_16_color_FFFFFF_t_70][]

这时有点懵，点击去查看源码发现确实是理解错误了，他并不包含最后一个【根据源码的例子可以看出】

sbustring源码：

/**
         * Returns a new string that is a substring of this string. The
         * substring begins at the specified <code>beginIndex</code> and
         * extends to the character at index <code>endIndex - 1</code>.
         * Thus the length of the substring is <code>endIndex-beginIndex</code>.
         * <p>
         * Examples:
         * <blockquote><pre>
         * "hamburger".substring(4, 8) returns "urge"
         * "smiles".substring(1, 5) returns "mile"
         * </pre></blockquote>
         *
         * @param      beginIndex   the beginning index, inclusive.
         * @param      endIndex     the ending index, exclusive.
         * @return     the specified substring.
         * @exception  IndexOutOfBoundsException  if the
         *             <code>beginIndex</code> is negative, or
         *             <code>endIndex</code> is larger than the length of
         *             this <code>String</code> object, or
         *             <code>beginIndex</code> is larger than
         *             <code>endIndex</code>.
         */
        public String substring(int beginIndex, int endIndex) {
            if (beginIndex < 0) {
                throw new StringIndexOutOfBoundsException(beginIndex);
            }
            if (endIndex > value.length) {
                throw new StringIndexOutOfBoundsException(endIndex);
            }
            int subLen = endIndex - beginIndex;
            if (subLen < 0) {
                throw new StringIndexOutOfBoundsException(subLen);
            }
            return ((beginIndex == 0) && (endIndex == value.length)) ? this
                    : new String(value, beginIndex, subLen);
        }

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