String 部分方法剖析

@Date:2018年08月13日16:55:06

split

将输入字符串断开成字符串对象数组，断开边界由正则表达式确定

替换操作

replace/replaceAll/appendReplacement 通过正则表达式来替换结果

compareTo(String anotherString)

基于每个字符的unicode编码值，比较两个字符串的字典顺序。小于零则

public int compareTo(String anotherString) {
        int len1 = value.length;
        int len2 = anotherString.value.length;
        int lim = Math.min(len1, len2);
        char v1[] = value;
        char v2[] = anotherString.value;

        int k = 0;
        while (k < lim) {
            char c1 = v1[k];
            char c2 = v2[k];
            if (c1 != c2) {
                return c1 - c2;
            }
            k++;
        }
        return len1 - len2;
    }

startsWith(String prefix, int toffset)

通过while循环判断当前字符串是否是在指定偏移量以指定前缀开头

public boolean startsWith(String prefix, int toffset) {
        char ta[] = value;
        int to = toffset;
        char pa[] = prefix.value;
        int po = 0;
        int pc = prefix.value.length;
        // Note: toffset might be near -1>>>1.
        if ((toffset < 0) || (toffset > value.length - pc)) {
            return false;
        }
        while (--pc >= 0) {
            if (ta[to++] != pa[po++]) {
                return false;
            }
        }
        return true;
    }

indexOf

得到指定字符串从指定索引开始哪个索引值

subString(int beginIndex , int endIndex)

返回一个字符串，该字符串是此字符串的子字符串。子字符串从指定的beginIndex开始，并扩展到索引endIndex - 1处的字符.
eg:String name = “zhuxiaolei” ; name = name.subString(4,8) = “iaol”;

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);
    }

String 部分方法剖析

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