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java - parseInt和valueOf的区别？

ringa_lee 2017-04-17 17:59:04

477

public class IntegerDemo4 {

public static void main(String[] args) { String str = "123"; int i = Integer.parseInt(str);

// int i = Integer.valueOf(str);

//parseInt和valueOf在这里用结果都对，但区别是什么呢？谢谢大家解答一下^_^

System.out.println(i+1); double d = Double.parseDouble(str); System.out.println(d+1); }

}

ringa_lee

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Peter_Zhu2017-04-17 18:01:04 3 floor

valueOf内部就用了parseInt，区别在于parseInt直接返回原始int类型数据；而valueOf又装了下箱，返回IntegerType.

There is another difference,parseInt期待输入是String，而valueOfis not

Feel the code:

public static int parseInt(String s) throws NumberFormatException { return parseInt(s,10); } public static Integer valueOf(String s, int radix) throws NumberFormatException { return Integer.valueOf(parseInt(s,radix)); } public static Integer valueOf(String s) throws NumberFormatException { return Integer.valueOf(parseInt(s, 10)); }

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Ty802017-04-17 18:01:04 2 floor

See source code:

//先调用parseInt获得int值，然后封装成Integer对象，注意封装的逻辑，有缓存 public static Integer valueOf(String s) throws NumberFormatException { return Integer.valueOf(parseInt(s, 10)); } public static Integer valueOf(int i) { assert IntegerCache.high >= 127; if (i >= IntegerCache.low && i <= IntegerCache.high) return IntegerCache.cache[i + (-IntegerCache.low)]; return new Integer(i); } //直接转换，获得int值 public static int parseInt(String s) throws NumberFormatException { return parseInt(s,10); }

In summary, generally use theInteger.parseInt(str)，除非你要返回Integertype, otherwise there will be packaging and unboxing, which will consume some performance.

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