System.out.println(0.3==0.1+0.1+0.1);

 System.out.println(0.5==0.1+0.1+0.1+0.1+0.1);//true
        System.out.println(0.5f==0.1f+0.1f+0.1f+0.1f+0.1f); //true

BigDecimal delta = BigDecimal.ONE.divide(BigDecimal.TEN);         // 0.1
BigDecimal n = BigDecimal.valueOf(100);
BigDecimal result = delta.multiply(n);                            // 10.0
BigDecimal number = BigDecimal.ZERO;                              // 0.0
for (int i = 0; i < n.intValue(); i++) {
	number = number.add(delta);                               // number += 0.1;
}
System.out.println(result.equals(number));                        // true
System.out.println(result.doubleValue() == number.doubleValue()); // true
System.out.println(result.floatValue() == number.floatValue());   // true

 public static void main(String[] args) { 
        try { 
            String value = "29.1"; 
            System.out.println((Float.valueOf(value) + 1.0) == 30.1); 
            System.out.println((Double.valueOf(value) + 1.0) == 30.1); 
            System.out.println(Float.valueOf(value)/0); 
            System.out.println(Double.valueOf(value)/0); 
        } 
        catch (NumberFormatException ex) { 
            System.out.println("NumberFormatException"); 
        } 
        catch (ArithmeticException ex) { 
            System.out.println("ArithmeticException"); 
        } 
    }