Java中BigDecimal的基本使用

//前提为a、b均不能为null
if(a.compareTo(b) == -1){
    System.out.println("a小于b");
}
 
if(a.compareTo(b) == 0){
    System.out.println("a等于b");
}
 
if(a.compareTo(b) == 1){
    System.out.println("a大于b");
}
 
if(a.compareTo(b) > -1){
    System.out.println("a大于等于b");
}
 
if(a.compareTo(b) < 1){
    System.out.println("a小于等于b");
}

BigDecimal bignum1 = new BigDecimal("1000"); 
BigDecimal bignum2 = new BigDecimal("300"); 
BigDecimal bignum3 = null; 

//加法 
bignum3 =  bignum1.add(bignum2); 
System.out.println("求和：" + bignum3);    

//减法 
bignum3 = bignum1.subtract(bignum2); 
System.out.println("求差：" + bignum); 

//乘法 
bignum3  = bignum1.multiply(bignum2); 
System.out.println("乘法积：" + bignum3); 
  
//除法 
bignum = bignum1.divide(bignum2); 
System.out.println("除法结果：" + bignum); 

     
    public static double div(String v1,String v2,int scale){ 
        if(scale<0){ 
            throw new IllegalArgumentException( 
                "The scale must be a positive integer or zero"); 
        } 
        BigDecimal b1 = new BigDecimal(v1); 
        BigDecimal b2 = new BigDecimal(v2); 
        return b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doublevalue(); 
    } 

     
    public static double round(double v,int scale){ 
        if(scale<0){ 
            throw new IllegalArgumentException( 
                "The scale must be a positive integer or zero"); 
        } 
        BigDecimal b = new BigDecimal(Double.toString(v)); 
        BigDecimal one = new BigDecimal("1"); 
        return b.divide(one,scale,BigDecimal.ROUND_HALF_UP).doublevalue(); 
    } 

	//提供类型转换
	BigDecimal b = new BigDecimal(v); 
    b.floatValue(); 
	b.intValue(); 


	 
    public static double returnMax(double v1,double v2){ 
    BigDecimal b1 = new BigDecimal(v1); 
    BigDecimal b2 = new BigDecimal(v2); 
        return b1.max(b2).doublevalue(); 
    } 

	 
    public static double returnMin(double v1,double v2){ 
    BigDecimal b1 = new BigDecimal(v1); 
    BigDecimal b2 = new BigDecimal(v2); 
        return b1.min(b2).doublevalue(); 
    } 

     
    public static int compareTo(double v1,double v2){ 
    BigDecimal b1 = new BigDecimal(v1); 
    BigDecimal b2 = new BigDecimal(v2); 
        return b1.compareTo(b2); 
    }