# Getting (back) into Java

### CS 3500, Fall 2019

# Example: Durations

# Analysis

What do we need to think about?

# Examples of durations

\(43.27 \mu s\)

\(10^9\) years

525,600 minutes

3 days, 6 hours, 17 minutes, and 25 seconds

# Object-oriented analysis

What might we do with them?

Convert units: 10 minutes = 600 seconds

Format: 257 seconds as

`4:17`

or`0:04:17`

Add: 2:45 plus 3:30 is 6:15

Subtract: 5 hours minus 2 hours is 3 hours

Decompose: 7868 as 2 hours, 11 minutes, and 8 seconds

Compare durations for equality and ordering

# Assumptions

Some simplifying assumptions:

Minimum time resolution: seconds

Lower bound: 0

Upper bound: unspecified

Unitless: 180 seconds is equal to 3 minutes

# Observers

```
long inSeconds();
String asHms();
```

```
int compareTo(Duration other);
boolean equals(Object other);
int hashCode();
```

# Operations

```
void add(Duration other);
void sub(Duration other);
```

# Operations

```
Duration plus(Duration other);
Duration minus(Duration other);
```

(We'll just do `plus`

.)

# Representation

Let's discuss.