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OneCodeOneTimeOneCodeOneTime
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Chapter 17 collections btp170722
1 parent 1e45cfa commit 0194f40

34 files changed

Lines changed: 1481 additions & 6 deletions

‎src/btp/oneP/AssociativeArray.java‎

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package btp.oneP;
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public class AssociativeArray<K,V>{
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public static void main(String[] args) {
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AssociativeArray<String,String> map = new AssociativeArray<String,String>(6);
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map.put("sky", "blue");
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map.put("grass", "green");
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map.put("ocean", "dancing");
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map.put("tree", "tall");
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map.put("earth", "brown");
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map.put("sun", "warm");
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try{
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map.put("extra", "object");
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}catch(Exception e){
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System.out.println(e);
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}
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System.out.println(map);
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System.out.println(map.get("ocean"));
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}
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private Object[][] pair;
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private int index;
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public AssociativeArray(int length){
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pair = new Object[length][2];
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}
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public void put(K key,V value){
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if(index >= pair.length){
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throw new ArrayIndexOutOfBoundsException();
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}
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pair[index++] = new Object[]{key,value};
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}
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@SuppressWarnings("unchecked")
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public V get(K key){
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for(int i=0;i<pair.length;i++){
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if(key.equals(pair[i][0])){
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return (V)pair[i][1];
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}
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}
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return null;
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}
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public String toString(){
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StringBuilder sb = new StringBuilder();
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for(int i=0;i<index;i++){
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sb.append(pair[i][0].toString());
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sb.append(" : ");
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sb.append(pair[i][1].toString());
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if(i<index-1){
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sb.append("\n");
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}
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}
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return sb.toString();
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}
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}

‎src/btp/oneP/Bits.java‎

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package btp.oneP;
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import java.util.BitSet;
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import java.util.Random;
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public class Bits {
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public static void printBitSet(BitSet b){
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System.out.println("bits: "+b);
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StringBuilder bbits = new StringBuilder();
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for(int j = 0;j < b.size();j++){
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bbits.append(b.get(j)?"1":"0");
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}
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System.out.println("bit pattern: "+bbits);
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}
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public static void main(String[] args) {
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// TODO Auto-generated method stub
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Random rand = new Random(47);
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byte bt = (byte)rand.nextInt();
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BitSet bb = new BitSet();
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for(int i = 7;i>=0;i--){
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if(((1 << i)&bt) != 0){
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bb.set(i);
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}else{
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bb.clear(i);
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}
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}
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System.out.println("byte value: "+bt);
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printBitSet(bb);
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short st = (short)rand.nextInt();
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BitSet bs = new BitSet();
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for(int i = 15;i>=0;i--){
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if(((1 << i)&st) != 0){
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bs.set(i);
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}else{
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bs.clear(i);
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}
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}
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System.out.println("short value: "+st);
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printBitSet(bs);
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int it = rand.nextInt();
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BitSet bi = new BitSet();
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for(int i = 31;i>=0;i--){
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if(((1 << i)&bt) != 0){
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bi.set(i);
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}else{
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bi.clear(i);
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}
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}
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System.out.println("int value: "+it);
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printBitSet(bi);
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BitSet b127 = new BitSet();
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b127.set(127);
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System.out.println("set bit 127: "+b127);
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BitSet b255 = new BitSet(65);
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b255.set(255);
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System.out.println("set bit 255: "+b255);
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BitSet b1023 = new BitSet(512);
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b1023.set(1023);
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b1023.set(1024);
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System.out.println("set bit 1023: "+b1023);
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}
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}

‎src/btp/oneP/CanonicalMapping.java‎

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package btp.oneP;
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import java.util.WeakHashMap;
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public class CanonicalMapping {
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public static void main(String[] args) {
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int size = 1000;
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if(args.length > 0){
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size = new Integer(args[0]);
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}
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Key[] keys = new Key[size];
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WeakHashMap<Key,Value> map = new WeakHashMap<Key,Value>();
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for(int i = 0;i < size; i++){
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Key k = new Key(Integer.toString(i));
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Value v = new Value(Integer.toString(i));
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if(i % 3 == 0){
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keys[i] = k;
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}
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map.put(k, v);
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}
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System.gc();
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}
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}

‎src/btp/oneP/ChangeCollectionTest.java‎

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package btp.oneP;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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public class ChangeCollectionTest {
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public static void main(String[] args) {
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List<String> list = new ArrayList<String>();
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list.add("hh");
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Iterator<String> it = list.iterator();
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//list.add("hh");
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while(it.hasNext()){
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it.remove();
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}
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}
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}

‎src/btp/oneP/CountedString.java‎

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package btp.oneP;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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public class CountedString {
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private static List<String> created = new ArrayList<String>();
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private String s;
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private int id = 0;
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public CountedString(String str){
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s = str;
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created.add(s);
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for(String s2:created){
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if(s2.equals(s)){
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id++;
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}
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}
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}
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public int hashCode(){
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int result = 17;
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result = 37*result+s.hashCode();
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result = 37*result+id;
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return result;
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}
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public boolean equals(Object o){
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return o instanceof CountedString && s.equals(((CountedString)o).s) && id==((CountedString)o).id;
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}
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@Override
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public String toString() {
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return "CountedString [s=" + s + ", id=" + id + "hashCode():"+hashCode()+"]";
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}
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public static void main(String[] args) {
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Map<CountedString,Integer> map = new HashMap<CountedString,Integer>();
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CountedString[] cs = new CountedString[5];
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for(int i=0;i<cs.length;i++){
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cs[i] = new CountedString("hi");
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map.put(cs[i], i);
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}
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System.out.println(map);
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for(CountedString cString:cs){
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System.out.print("Looking up "+cString);
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System.out.println(map.get(cString));
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}
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}
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}

‎src/btp/oneP/DequeTest.java‎

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package btp.oneP;
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import java.util.LinkedList;
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public class DequeTest {
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static void fillTest(Deque<Integer> deque){
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for(int i = 20;i < 27;i++){
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deque.addFirst(i);
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}
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for(int i = 50;i < 55;i++){
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deque.addLast(i);
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}
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}
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public static void main(String[] args) {
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Deque<Integer> di = new Deque<Integer>();
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fillTest(di);
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System.out.println(di);
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while(di.size() != 0){
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System.out.print(di.removeFirst()+" ");
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}
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System.out.println();
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fillTest(di);
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while(di.size() != 0){
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System.out.print(di.removeLast()+" ");
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}
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System.out.println();
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}
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}
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class Deque<T>{
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private LinkedList<T> deque = new LinkedList<T>();
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public void addFirst(T t){
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deque.add(t);
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}
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public void addLast(T t){
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deque.addLast(t);
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}
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public T getFirst(){
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return deque.getFirst();
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}
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public T getLast(){
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return deque.getLast();
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}
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public T removeFirst(){
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return deque.removeFirst();
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}
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public T removeLast(){
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return deque.removeLast();
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}
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public int size(){
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return deque.size();
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}
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public String toString(){
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return deque.toString();
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}
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}

‎src/btp/oneP/Element.java‎

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package btp.oneP;
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public class Element {
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private String ident;
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public Element(String id){
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ident = id;
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}
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public String toString(){
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return ident;
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}
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public int hashCode(){
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return ident.hashCode();
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}
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public boolean equals(Object r){
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return r instanceof Element && ident.equals(((Element)r).ident);
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}
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protected void finalize(){
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System.out.println("Finalizing "+this.getClass().getSimpleName()+" "+ident+":"+(Integer.parseInt(ident)%3==0));
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}
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}

‎src/btp/oneP/Enumerations.java‎

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package btp.oneP;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Enumeration;
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import java.util.Vector;
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public class Enumerations {
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public static void main(String[] args) {
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Vector<String> v = new Vector<String>(Countries.names(10));
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Enumeration<String> e = v.elements();
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while(e.hasMoreElements()){
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System.out.println(e.nextElement()+", ");
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}
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e = Collections.enumeration(new ArrayList<String>());
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}
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}

‎src/btp/oneP/FailFast.java‎

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package btp.oneP;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.ConcurrentModificationException;
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import java.util.Iterator;
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public class FailFast {
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public static void main(String[] args) {
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Collection<String> c = new ArrayList<String>();
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Iterator<String> it = c.iterator();
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c.add("An object");
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try{
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String s = it.next();
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}catch(ConcurrentModificationException e){
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System.out.println(e);
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}
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}
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}

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