JavaSE8基础 String substring 返回字符串中指定索引值区间内的字符

os ：windows7 x64
    jdk：jdk-8u131-windows-x64
    ide：Eclipse Oxygen Release (4.7.0)
    
    
code：

package jizuiku.t00;

public class Demo5 {
	public static void main(String[] args) {

		//索引值                   012345
		String str = "abc01234543210cba";
		int beginIndex = 2;
		int endIndex = 5;//不包括这个索引所对应的字符,为啥?看看源代码,你就知道.
		System.out.println(str.substring(beginIndex, endIndex));
	}
}

result：

scoureCode：

    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);
    }