java基础数据类型的包装类

水深无声 2022-04-06 09:38 251阅读 0赞

# 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>