public class TestList {    public static void main(String agrs[]) {        List l1 = new LinkedList();        for (int i = 0; i <= 5; i++) {            l1.add("a" + i);        }        System.out.PRintln(l1);        l1.add(3, "a100");        System.out.println(l1);        l1.set(6, "a200");        System.out.println(l1);        System.out.print((String) l1.get(2) + " ");        System.out.println(l1.indexOf("a3"));        l1.remove(1);        System.out.println(l1);    }}
結(jié)果是：
[a0, a1, a2, a3, a4, a5]
[a0, a1, a2, a100, a3, a4, a5][a0, a1, a2, a100, a3, a4, a200]a2   4[a0, a2, a100, a3, a4, a200]?2.List常用算法?類java.util.Collections提供了一些靜態(tài)方法實(shí)現(xiàn)了基于List容器的一些常用算法。?void sort(List)                             對(duì)List容器內(nèi)的元素排序?void shuffle(List)                        對(duì)List容器內(nèi)的對(duì)象進(jìn)行隨機(jī)排序?void reverse(List)                      對(duì)List容器內(nèi)的對(duì)象進(jìn)行逆序排序?void fill(List,Object)                   用一個(gè)特定的對(duì)象重寫整個(gè)List容器?void copy(List dest,List src)    將src List容器內(nèi)容拷貝到dest List容器?int binarySearch(List,Object)  對(duì)于順序的List容器，采用折半查找的方法查找特定對(duì)象?算法舉例：
public class TestList {    public static void main(String agrs[]) {        List l1 = new LinkedList();        List l2 = new LinkedList();        for (int i = 0; i <= 9; i++) {            l1.add("a" + i);        }        System.out.println(l1);        Collections.shuffle(l1); //隨機(jī)排序        System.out.println(l1);        Collections.reverse(l1); //逆序        System.out.println(l1);        Collections.sort(l1); //排序        System.out.println(l1);        System.out.println(Collections.binarySearch(l1, "a5")); //折半查找    }}結(jié)果是：[a0, a1, a2, a3, a4, a5, a6, a7, a8, a9][a6, a8, a9, a1, a2, a5, a0, a3, a4, a7][a7, a4, a3, a0, a5, a2, a1, a9, a8, a6][a0, a1, a2, a3, a4, a5, a6, a7, a8, a9]53.Comparable接口?所有可以“排序“的類都實(shí)現(xiàn)了java.lang.Comparable接口，comparable接口中只有一個(gè)方法public int compareTo(Object obj);該方法：?返回0表示this==obj，正數(shù)this>obj，負(fù)數(shù)this實(shí)現(xiàn)了Comparable接口的類通常實(shí)現(xiàn)comparaTo方法從而確定該類對(duì)象的排序方式。?將上述的Name類改寫：class Name implements Comparable加入
public int compareTo(Object o) {Name n = (Name)o;int lastCmp =c.compareTo(n.c);return(lastCmp!=0 ? lastCmp :s.compareTo(n.s));}?然后運(yùn)行：
public class TestComparable {    public static void main(String agrs[]) {        List l1 = new LinkedList();        l1.add(new Name("Karl", "M"));        l1.add(new Name("Steven", "Lee"));        l1.add(new Name("John", "O"));        l1.add(new Name("Tom", "M"));        System.out.println(l1);        Collections.sort(l1);        System.out.println(l1);    }}結(jié)果是：[Karl M, Steven Lee, John O, Tom M]
[Steven Lee, Karl M, Tom M, John O]
?4.如何選擇數(shù)據(jù)結(jié)構(gòu)?衡量標(biāo)準(zhǔn)：讀的效率和改的效率?
Array讀快改慢，Linked改快讀慢，Hash兩者之間?
5.Map接口?實(shí)現(xiàn)Map接口的類用來存儲(chǔ) 鍵—值 對(duì)。?Map接口的實(shí)現(xiàn)類有HashMap(哈希表)和TreeMap(二叉樹)等?。?二叉樹：在計(jì)算機(jī)科學(xué)中，二叉樹是每個(gè)節(jié)點(diǎn)最多有兩個(gè)子樹的樹結(jié)構(gòu)。通常子樹被稱作左子樹（left subtree）和右子樹（right subtree）。二叉樹常被用于實(shí)現(xiàn)二叉查找樹和二叉堆。二叉樹的每個(gè)結(jié)點(diǎn)至多只有二棵子樹(不存在度大于2的結(jié)點(diǎn))。二叉樹的子樹有左右之分，次序不能顛倒。二叉樹的第i層至多有2^{i-1}個(gè)結(jié)點(diǎn)；深度為k的二叉樹至多有2^k-1個(gè)結(jié)點(diǎn)；對(duì)任何一棵二叉樹T，如果其終端結(jié)點(diǎn)數(shù)為n_0，度為2的結(jié)點(diǎn)數(shù)為n_2，則n_0=n_2+1。一棵深度為k，且有2^k-1個(gè)節(jié)點(diǎn)稱之為滿二叉樹；深度為k，有n個(gè)節(jié)點(diǎn)的二叉樹，當(dāng)且僅當(dāng)其每一個(gè)節(jié)點(diǎn)都與深度為k的滿二叉樹中，序號(hào)為1至n的節(jié)點(diǎn)對(duì)應(yīng)時(shí)，稱之為完全二叉樹。?哈希表：?散列表（Hash table，也叫哈希表），是根據(jù)關(guān)鍵碼值(Key value)而直接進(jìn)行訪問的數(shù)據(jù)結(jié)構(gòu)。也就是說，它通過把關(guān)鍵碼值映射到表中一個(gè)位置來訪問記錄，以加快查找的速度。這個(gè)映射函數(shù)叫做散列函數(shù)，存放記錄的數(shù)組叫做散列表。給定表M，存在函數(shù)f(key)，對(duì)任意給定的關(guān)鍵字值key，代入函數(shù)后若能得到包含該關(guān)鍵字的記錄在表中的地址，則稱表M為哈希(Hash）表，函數(shù)f(key)為哈希(Hash) 函數(shù)。Map類中存儲(chǔ)的鍵—值對(duì)通過鍵來標(biāo)識(shí)，所以鍵值不能重復(fù)。?Object put(Object key,Object value);       //放入一對(duì)東西?，返回原key的valueObject get(Object key);                              //通過key找到value?Object remove(Object key);?                      //去掉key對(duì)應(yīng)的value，key隨之也去掉boolean containsKey(object key);?           //是不是包含keyboolean containsKey(object value);int size();                                                       多少對(duì)boolean isEmpty()void putAll?(Map t);                                       把另一個(gè)Map所有值加進(jìn)來?void clear();??例：
public class TestMap {    public static void main(String agrs[]) {        Map m1 = new HashMap();        Map m2 = new TreeMap();        m1.put("one", new Integer(1));        m1.put("two", new Integer(2));        m1.put("three", new Integer(3));        m2.put("A", new Integer(1));        m2.put("B", new Integer(2));        System.out.println(m1.size());        System.out.println(m1.containsKey("one"));        System.out.println(m2.containsValue(new Integer(1)));        if (m1.containsKey("two")) {            int i = ((Integer) m1.get("two")).intValue();//get two返回的是object，強(qiáng)制轉(zhuǎn)換成integer，然后獲得int的值            System.out.println(i);        }        Map m3 = new HashMap(m1);        m3.putAll(m2);        System.out.println(m3);    }}結(jié)果是：3truetrue2{A=1, B=2, two=2, three=3, one=1}?6.Auto-boxing/unboxing?在合適的時(shí)機(jī)自動(dòng)打包，解包，自動(dòng)將基礎(chǔ)類型轉(zhuǎn)換成對(duì)象，自動(dòng)將對(duì)象轉(zhuǎn)換成基礎(chǔ)類型?
public class TestMap {    public static void main(String agrs[]) {        Map m1 = new HashMap();        Map m2 = new TreeMap();        m1.put("one", 1);         //打包        m1.put("two", 2);        m1.put("three", 3);        m2.put("A", 1);        m2.put("B", 2);        System.out.println(m1.size());        System.out.println(m1.containsKey("one"));        System.out.println(m2.containsValue(1));        if (m1.containsKey("two")) {            int i = ((Integer) m1.get("two"));   //Integer是不能去掉的，對(duì)象轉(zhuǎn)換成Integer后，才能自動(dòng)轉(zhuǎn)換成int類型            System.out.println(i);        }        Map m3 = new HashMap(m1);        m3.putAll(m2);        System.out.println(m3);    }}
將TestMap加以修改，結(jié)果相同
 7.泛型?JDK1.4以前類型不明確：裝入集合的類型都被當(dāng)成Object對(duì)待從而失去自己的實(shí)際類型。解決辦法：在定義集合的時(shí)候同時(shí)定義集合中對(duì)象的類型。?示例：BasicGeneric，可以在定義Collection時(shí)定義，也可以在循環(huán)時(shí)用Iterator指定?舉例：
public class BasicGeneric {    public static void main(String agrs[]) {        List c = new ArrayList();        c.add("aaa");        c.add("bbb");        c.add("ccc");        for (int i = 0; i < c.size(); i++) {            String s = c.get(i).toString();            System.out.println(s);        }        Collection c2 = new HashSet();        c2.add("AAA");        c2.add("BBB");        c2.add("CCC");        for (Iterator it = c2.iterator(); it.hasNext();){            String s = it.next().toString();            System.out.println(s);        }    }}
public class MyName implements Comparable<MyName>{//對(duì)MyName類用泛型實(shí)現(xiàn)comparable    int age;    public int compareTo(MyName nm) {        if(this.age > nm.age) return 1;        else if(this.age < nm.age) return -1;        else return 0;    }}結(jié)果是：aaa   bbb  ccc  AAA  CCC  BBB泛型和打包綜合利用：?
public class TestMap {    public static void main(String agrs[]) {        Map m1 = new HashMap();        m1.put("one", 1);        m1.put("two", 2);        m1.put("three", 3);        System.out.println(m1.size());        System.out.println(m1.containsKey("one"));        if (m1.containsKey("two")) {            int i = (int) m1.get("two");            System.out.println(i);        }    }}結(jié)果是：3true2?另一個(gè)例子：?
public class TestArgsWords {    private static final int ONE = 1;    public static void main(String args[]) {        Map m = new HashMap();        for (int i = 0; i < args.length; i++) {            if (!m.containsKey(args[i])) {                m.put(args[i], ONE);            } else {                int freq = (int) m.get(args[i]);                m.put(args[i], freq + 1);            }        }        System.out.println                (m.size() + " distinct words detected:");        System.out.println(m);    }}結(jié)果：0  distinct words detected:?{}