Generics - Bounded Type Parameters In Classes And Methods

Java

by techbard 2016. 7. 10. 10:06

# Animal.java

public class Animal implements Comparable<Animal> {

private String name;

public Animal() {
}

public Animal(String name) {
this.name = name;
}

public String getName() {
return name;
}

@Override
public String toString() {
return String.format("%s\n", this.name);
}

@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}

if (!(obj instanceof Animal)) {
return false;
}

return (this.getName().equals(((Animal) obj).getName()));
}

@Override
public int compareTo(Animal o) {
if (o == null)
return 1;

// Strings are comparable.
int cmpValue = this.getName().compareTo(o.getName());

if (cmpValue < 0)
return 1;
if (cmpValue > 0)
return -1;

return 0;
}
}

# BestDataContainer.java

import java.util.NoSuchElementException;

public class BestDataContainer<T extends Comparable<? super T>> {

private Object[] data;
public int countItems;

public BestDataContainer() {
this(10);
}

public BestDataContainer(int capacity) {
data = new Object[capacity];
countItems = 0;
}

public int size() {
return countItems;
}

public boolean add(T item) {
if (item == null) {
return false;
}

if (countItems == data.length) {
return false;
}

int itemIndex = findItem(item);
if (itemIndex > 0) {
return false;
}

data[countItems++] = item;
return true;
}

public boolean remove(int index) {
validateIndex(index);
int i = index;
int j = i + 1;

while (j < countItems) {
data[j - 1] = data[j];
j++;
}
countItems--;
return true;
}

public boolean remove(T item) {
if (item == null) {
return false;

}

int index = findItem(item);
if (index < 0) {
return false;
}

return remove(index);
}

public int findItem(T item) {
for (int i = 0; i < countItems; i++) {
if (data[i].equals(item)) {
return i;
}
}

return -1;
}

public T get(int index) {
validateIndex(index);
return (T) data[index];
}

private void validateIndex(int index) {
if (index < 0 || index >= countItems) {
throw new NoSuchElementException("Invalid Index");
}
}

@Override
public String toString() {
StringBuilder sb = new StringBuilder();

for (int i = 0; i < countItems; i++) {
sb.append("Next Item: " + data[i] + "\n");
}

return sb.toString();
}

public T getMax() {
if (countItems > 0) {
T max = (T) data[0];
for (int i = 1; i < countItems; i++) {
max = BestDataContainer.getMax(max, (T) data[i]);
}

return max;
} else if (countItems == 0) {
return (T) data[0];
}

return null;
}

public T getMin() {
if (countItems > 0) {
T min = (T) data[0];
for (int i = 1; i < countItems; i++) {
min = BestDataContainer.getMin(min, (T) data[i]);
}

return min;
} else if (countItems == 0) {
return (T) data[0];
}

return null;
}

public static <T extends Comparable<? super T>> T getMax(T o1, T o2) {
return (o1.compareTo(o2)) == 1 ? o1 : o2;
}

public static <T extends Comparable<? super T>> T getMin(T o1, T o2) {
return (o1.compareTo(o2)) == 1 ? o2 : o1;
}
}

# Zoo.java

public class Zoo {

public static void main(String[] args) {
BestDataContainer<Animal> bdc = new BestDataContainer<>();

bdc.add(new Animal("Chipmunk"));
bdc.add(new Animal("Hedgehog"));
bdc.add(new Animal("Dog"));
bdc.add(new Animal("Frog"));
bdc.add(new Animal("Eagele"));

System.out.println(bdc);
System.out.println("====================");

System.out.println("Max: " + bdc.getMax());
System.out.println("Min: " + bdc.getMin());
}
}

# 결과

Next: Item: Chipmunk

Next: Item: Hedgehog

Next: Item: Dog

Next: Item: Frog

Next: Item: Eagele

====================
Max: Chipmunk

Min: Hedgehog