java基础数据类型的包装类
基本数据类型 -------------> 对应的包装类
byte Byte
short Short
int Integer
long Long
float Float
double Double
char Character
boolean Boolean
TestWrapperClass.java
//基本数据类型的包装类测试 /* byte Byte short Short int Integer long Long float Float double Double char Character boolean Boolean */ public class TestWrapperClass { public static void main(String[] args) { /* Double(double value) Constructs a newly allocated Double object that represents the primitive double argument. Double(String s) Constructs a newly allocated Double object that represents the floating-point value of type double represented by the string. */ Integer i = new Integer(100); Double d = new Double("123.456"); int j = i.intValue() + d.intValue(); float f = i.floatValue() + d.floatValue(); System.out.println(j);//223 System.out.println(f);//223.456 double pi = Double.parseDouble("3.1415926"); double r = Double.valueOf("2.0").doubleValue(); double s = pi * r * r; System.out.println(s);//12.5663704 int k; try{ k = Integer.parseInt("1.25");//只能是整数字符串 }catch(NumberFormatException e){ k = -1; System.out.println("数据格式不正确: " + k);//数据格式不正确: -1 } /* static String toBinaryString(int i) Returns a string representation of the integer argument as an unsigned integer in base 2. static String toHexString(int i) Returns a string representation of the integer argument as an unsigned integer in base 16. static String toOctalString(int i) Returns a string representation of the integer argument as an unsigned integer in base 8. */ System.out.println(Integer.toBinaryString(123) + "B");//1111011B 二进制 System.out.println(Integer.toHexString(123) + "H");//7bH 十六进制 System.out.println(Integer.toOctalString(123) + "O");//173O 八进制 } }
F:\java>javac TestWrapperClass.java F:\java>java TestWrapperClass 223 223.456 12.5663704 数据格式不正确: -1 1111011B 7bH 173O F:\java>