1. 使用原生java方式
public boolean isPalindrome(String text) { String clean = text.replaceAll("\\s+", "").toLowerCase(); int length = clean.length(); int forward = 0; int backward = length - 1; while (backward > forward) { char forwardChar = clean.charAt(forward++); char backwardChar = clean.charAt(backward--); if (forwardChar != backwardChar) return false; } return true; }
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2. 使用字符串reverse比较
public boolean isPalindromeReverseTheString(String text) { StringBuilder reverse = new StringBuilder(); String clean = text.replaceAll("\\s+", "").toLowerCase(); char[] plain = clean.toCharArray(); for (int i = plain.length - 1; i >= 0; i--) { reverse.append(plain[i]); } return (reverse.toString()).equals(clean); }
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3. 使用stringbuffer 和stringbuilder直接翻转字符串比较
public boolean isPalindromeUsingStringBuilder(String text) { String clean = text.replaceAll("\\s+", "").toLowerCase(); StringBuilder plain = new StringBuilder(clean); StringBuilder reverse = plain.reverse(); return (reverse.toString()).equals(clean); } public boolean isPalindromeUsingStringBuffer(String text) { String clean = text.replaceAll("\\s+", "").toLowerCase(); StringBuffer plain = new StringBuffer(clean); StringBuffer reverse = plain.reverse(); return (reverse.toString()).equals(clean); }
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4. 使用java8 intStream
public boolean isPalindromeUsingIntStream(String text) { String temp = text.replaceAll("\\s+", "").toLowerCase(); return IntStream.range(0, temp.length() / 2) .noneMatch(i -> temp.charAt(i) != temp.charAt(temp.length() - i - 1)); }
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5. 使用递归调用
public boolean isPalindromeRecursive(String text){ String clean = text.replaceAll("\\s+", "").toLowerCase(); return recursivePalindrome(clean,0,clean.length()-1); } private boolean recursivePalindrome(String text, int forward, int backward) { if (forward == backward) { return true; } if ((text.charAt(forward)) != (text.charAt(backward))) { return false; } if (forward < backward + 1) { return recursivePalindrome(text, forward + 1, backward - 1); } return true; }
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总结: 回文数验证分两种 一种是移动下标比较 另一种是 翻转 比较,翻转比较性能没有下标比较好,
所以建议使用java8 InStreannomatch方法