Generic Methods

Java

by techbard 2016. 7. 8. 21:45

package GenericMethods;

import java.util.Random;

public class Driver {

private static final int SIZE = 10;

public static void main(String[] args) {
// we CANT'Y use primitive types in Generics!

Integer[] myInts;
myInts = new Integer[SIZE];

Random r = new Random();

for (int i = 0; i < myInts.length; i++) {
myInts[i] = r.nextInt(SIZE);
}

for (Integer myInt : myInts) {
System.out.println(myInt);
}

swapItems(0, 1, myInts);
System.out.println("==============================");

for (Integer myInt : myInts) {
System.out.println(myInt);
}
}

public static <T> void swapItems(int i1, int i2, T[] items) {
T temp = items[i1];
items[i1] = items[i2];
items[i2] = temp;
}

public static <T> void printItems(T[] items) {
for (T item : items) {
System.out.println("Next " + item.getClass().getName() + ": " + item);
}
}
}

# 결과

9
2
3
1
7
4
6
9
2
8
==============================
2
9
3
1
7
4
6
9
2
8

# Animal.java

public class 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, %s\n", getClass(), this.name);
}
}

# GernMethod.java

public class GernMethods {

private static final int MAX = 5;

public static void main(String[] args) {

intSwapTest();

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

animalSwapTest();
}

private static void animalSwapTest() {
Animal[] myAnimals = new Animal[MAX];

for (int i = 0; i < MAX; i++) {
myAnimals[i] = new Animal(String.valueOf(i));
}

swapItem(0, 1, myAnimals);

for (Animal myAnimal : myAnimals) {
System.out.println(myAnimal.getName());
}
}

private static void intSwapTest() {
Integer[] myInts;

myInts = new Integer[MAX];

for (int i = 0; i < MAX; i++) {
myInts[i] = i;
}

swapItem(0, 1, myInts);

for (Integer myInt : myInts) {
System.out.println(myInt);
}
}

private static <T> void swapItem(int i1, int i2, T[] items) {
T temp = items[i1];
items[i1] = items[i2];
items[i2] = temp;
}

}

# 결과

1
0
2
3
4
====================
Item: 1 instance.
Item: 0 instance.
Item: 2 instance.
Item: 3 instance.
Item: 4 instance.