Groovy grammar learning (5) operator overloading

Groovy also has the function of operator overloading. In fact, operators also call specific methods in the class. Using operators looks more concise and easy to understand.
Simple overloading for a subtraction

class Money{
    def number

    def  minus(o){
        if(o instanceof Money){
            number-=o.number
        }else if(o instanceof Number){
            number-=o
        }
        this
    }


    @Override
    public String toString() {
        return "Money{" +
                "number=" + number +
                '}';
    }
}

def m=new Money(number: 100)
def b=new Money(number: 50)

println m-b
println m-30

result:

Money{number=50}
Money{number=20}

The table of operator overloading is attached below, you can check it yourself, the original blog address https://www.cnblogs.com/rollenholt/archive/2013/10/02/3349047.html

The following table describes the methods to which operators in groovy map:

Operator	Method
a + b	a.plus(b)
a – b	a.minus(b)
a * b	a.multiply(b)
a ** b	a.power(b)
a / b	a.div(b)
a % b	a.mod(b)
a | b	a.or(b)
a & b	a.and(b)
a ^ b	a.xor(b)
a++ or ++a	a.next()
a– or –a	a.previous()
a[b]	a.getAt(b)
a[b] = c	a.putAt(b, c)
a << b	a.leftShift(b)
a >> b	a.rightShift(b)
switch(a) { case(b) : }	b.isCase(a)
~a	a.bitwiseNegate()
-a	a.negative()
+a	a.positive()

In addition, it should be noted that all the following operators will not throw java.lang.NullPointerException when they encounter null

Operator	Method
a == b	a.equals(b) or a.compareTo(b) == 0 **
a != b	! a.equals(b)
a <=> b	a.compareTo(b)
a > b	a.compareTo(b) > 0
a >= b	a.compareTo(b) >= 0
a < b	a.compareTo(b) < 0
a <= b	a.compareTo(b) <= 0

Note that the "==" operator is not always equivalent to the equals() method.

比如：
    def a = null
    def b = "foo"

    assert a != b
    assert b != a
    assert a == null

No matter whether a or b is null, java.lang.NullPointerException will not be thrown.

In addition, when comparing objects of different types, the coercion rules are used to convert the numeric type to the largest numeric type. So the following code is valid:

    Byte a = 12
    Double b = 10

    assert a instanceof Byte
    assert b instanceof Double

    assert a > b