TA貢獻2016條經驗 獲得超9個贊
不知道你說的實現是怎么個實現？如果只是調用的話 str.subString(begin,end)就可以了，如果是java的底層實現的話，下面是來自java.lang.String的代碼:
public String substring(int beginIndex, int endIndex) { if (beginIndex < 0) { throw new StringIndexOutOfBoundsException(beginIndex); } if (endIndex > count) { throw new StringIndexOutOfBoundsException(endIndex); } if (beginIndex > endIndex) { throw new StringIndexOutOfBoundsException(endIndex - beginIndex); } return ((beginIndex == 0) && (endIndex == count)) ? this : new String(offset + beginIndex, endIndex - beginIndex, value); } |
然后調用String的一個私有構造器:
// Package private constructor which shares value array for speed. String(int offset, int count, char value[]) { this.value = value; this.offset = offset; this.count = count; } |
TA貢獻1865條經驗 獲得超7個贊
給你個例子,你參考下
public class $ { public static void main(String[] args) { String str = "abcdefg"; System.out.println(substring(str, 0, 1)); } private static String substring(String str, int begin, int end) { char[] ch = str.toCharArray(); StringBuffer buf = new StringBuffer(); for (int i = begin; i < end; i++) { buf.append(ch[i]); } return buf.toString(); }} |
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