练习一:
class Gerbil {
int gerbilNumber;
public Gerbil(int i) {
gerbilNumber = i;
}
public void hop() {
print("Gerbil" + gerbilNumber + "hops");
}
}
public class Ex11_1 {
public static void main(String[] args) {
ArrayList<Gerbil> gb = new ArrayList<Gerbil>();
for(int i = 0; i < 10; i++) {
gb.add(new Gerbil(i));
}
for(int i = 0; i < 10; i++) {
gb.get(i).hop();
}
for(Gerbil g : gb) {
g.hop();
}
}
}
练习二:
public class Ex2 {
public static void main(String[] args) {
Set<Integer> c = new HashSet<Integer>();
for(int i = 0; i < 10; i++)
c.add(i); // Autoboxing
for(Integer i : c)
System.out.print(i + ", ");
}
}
练习四:
package com.tutorialspoit;
import java.util.Connection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.TreeSet;
import static com.tutorialspoit.Print.*;
class Generator {
int key = 0;
public String next() {
switch(key) {
default:
case 0 : key++; return "Snow White";
case 1 : key++; return "Bashful";
case 2 : key++; return "Doc";
case 3 : key++; return "Dopey";
case 4 : key++; return "Grumpy";
case 5 : key++; return "Happy";
case 6 : key++; return "Sleepy";
case 7 : key = 0; return "Sneezy";
}
}
public void fillA(String[] a) {
for(int i = 0; i < a.length; i++) {
a[i] = next();
}
}
public Collection fill(Collection<String> c,int n) {
for(int i = 0; i < n; i++)
c.add(next());
return c;
}
}
public class Ex11_4 {
public static void main(String[] args) {
Generator gen = new Generator();
String[] a = new String[10];
gen.fillA(a);
for(String s : a) print(s + " ");
print();
print(gen.fill(new ArrayList<String>(),10));
print(gen.fill(new LinkedList<String>(),10));
print(gen.fill(new HashSet<String>(),10));
print(gen.fill(new LinkedHashSet<String>(),10));
print(gen.fill(new TreeSet<String>(),10));
}
}
练习五: