Java 必知必会 第 6 篇

如何将String转换为Int

有两种方式

Integer x = Integer.valueOf(str);
// or
int y = Integer.parseInt(str);

这两种方式有一点点不同：

  • valueOf返回的是java.lang.Integer的实例
  • parseInt返回的是基本数据类型 int

Short.valueOf/parseShort,Long.valueOf/parseLong等也是有类似差别。

另外还需注意的是，在做int类型转换时，可能会抛出NumberFormatException，因此要做好异常捕获

int foo;
String StringThatCouldBeANumberOrNot = "26263Hello"; //will throw exception
String StringThatCouldBeANumberOrNot2 = "26263"; //will not throw exception
try {
      foo = Integer.parseInt(StringThatCouldBeANumberOrNot);
} catch (NumberFormatException e) {
      //Will Throw exception!
      //do something! anything to handle the exception.
}

try {
      foo = Integer.parseInt(StringThatCouldBeANumberOrNot2);
} catch (NumberFormatException e) {
      //No problem this time but still it is good practice to care about exceptions.
      //Never trust user input :)
      //do something! anything to handle the exception.
}