Java的基础知识三

import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;public class myArrayList {
public static void main(String[] args){
List<String> list = new ArrayList<String>();
list.add("nick");
list.add("jenny");
list.add("Maria"); //第一种遍历方法使用foreach遍历List
for (String str : list){
System.out.println(str);
} //第二种遍历，把链表变为数组相关的内容进行遍历
String[] strArray = new String[list.size()];
list.toArray(strArray);
for (int i=0;i<strArray.length;i++){
System.out.println(strArray[i]);
} //第三种遍历 使用迭代器进行相关遍历
Iterator<String> ite=list.iterator();
while (ite.hasNext()){
System.out.println(ite.next());
}
}
}

package three;import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;public class mymap {
public static void main(String[] args){
Map<String, String> map = new HashMap<String, String>();
map.put("name", "nick");
map.put("age", "18");
map.put("single", "singleDog"); //第一种：普遍使用，二次取值
for (String key : map.keySet()){
System.out.println(key + " " + map.get(key));
} //通过Map.entrySet使用iterator遍历key和value
Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, String> entry = it.next();
System.out.println(entry.getKey() + " " + entry.getValue());
} //第三种：推荐，尤其是容量大时
for (Map.Entry<String, String> entry : map.entrySet()){
System.out.println(entry.getKey() + " " + entry.getValue());
} //通过Map.values()遍历所有的value，但不能遍历key
for (String v : map.values()){
System.out.println(v);
}
}
}

package three;import java.util.Vector;
import java.util.Enumeration;public class myEnumeration {
public static void main(String[] args){
Enumeration days;
Vector dayNames = new Vector();
dayNames.add("Sunday");
dayNames.add("Monday");
dayNames.add("Tuesday");
dayNames.add("Wednesday");
dayNames.add("Thursday");
dayNames.add("Friday");
dayNames.add("Saturday");
days = dayNames.elements();
while (days.hasMoreElements()){
System.out.println(days.nextElement());
}
}
}

package three;import java.util.BitSet;public class myBitset {
public static void main(String[] args){
BitSet bits1 = new BitSet(16);
BitSet bits2 = new BitSet(16); // set some bits
for(int i=0; i<16; i++) {
if((i%2) == 0) bits1.set(i);
if((i%5) != 0) bits2.set(i);
}
System.out.println("Initial pattern in bits1: ");
System.out.println(bits1); // {0, 2, 4, 6, 8, 10, 12, 14}
System.out.println("\nInitial pattern in bits2: ");
System.out.println(bits2); // {1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14} // AND bits
bits2.and(bits1);
System.out.println("\nbits2 AND bits1: ");
System.out.println(bits1); // {0, 2, 4, 6, 8, 10, 12, 14}
System.out.println(bits2); // {2, 4, 6, 8, 12, 14} // OR bits
bits2.or(bits1);
System.out.println("\nbits2 OR bits1: ");
System.out.println(bits1); // {0, 2, 4, 6, 8, 10, 12, 14}
System.out.println(bits2); // {0, 2, 4, 6, 8, 10, 12, 14} // XOR bits
bits2.xor(bits1);
System.out.println("\nbits2 XOR bits1: ");
System.out.println(bits1); // {0, 2, 4, 6, 8, 10, 12, 14}
System.out.println(bits2); // {}
}
}

package three;import java.util.*;public class myVector {
public static void main(String[] args){
Vector v = new Vector(3, 2);
System.out.println(v.size()); //
System.out.println(v.capacity()); //
v.addElement(new Integer(1));
System.out.println(v.capacity()); //
v.addElement(new Integer(2));
System.out.println(v.capacity()); //
v.addElement(new Integer(3));
System.out.println(v.capacity()); // v.addElement(new Integer(4));
System.out.println(v.capacity()); //
v.addElement(new Double(5.45));
System.out.println(v.capacity()); // v.addElement(new Double(6.08));
v.addElement(new Integer(7));
System.out.println(v.capacity()); //
v.addElement(new Float(9.4));
v.addElement(new Integer(10));
System.out.println(v.capacity()); //
v.addElement(new Integer(11));
v.addElement(new Integer(12));
System.out.println(v.capacity()); //
System.out.println((Integer)v.firstElement()); //
System.out.println((Integer)v.lastElement()); // if(v.contains(new Integer(3)))
System.out.println("Vector contains 3."); //true // enumerate the elements in the vector.
Enumeration vEnum = v.elements();
System.out.println("\nElements in vector:");
while(vEnum.hasMoreElements())
System.out.print(vEnum.nextElement() + " ");
// 1 2 3 4 5.45 6.08 7 9.4 10 11 12
System.out.println();
}
}

package three;import java.util.*;public class myStack {
static void showpush(Stack st, int a) {
st.push(new Integer(a));
System.out.println("push(" + a + ")");
System.out.println("stack: " + st);
} static void showpop(Stack st) {
System.out.print("pop -> ");
Integer a = (Integer) st.pop();
System.out.println(a);
System.out.println("stack: " + st);
} public static void main(String args[]) {
Stack st = new Stack();
System.out.println("stack: " + st);
showpush(st, 42);
showpush(st, 66);
showpush(st, 99);
showpop(st);
showpop(st);
showpop(st);
try {
showpop(st);
} catch (EmptyStackException e) {
System.out.println("empty stack");
}
}
/*输出结果:
stack: []
push(42)
stack: [42]
push(66)
stack: [42, 66]
push(99)
stack: [42, 66, 99]
pop -> 99
stack: [42, 66]
pop -> 66
stack: [42]
pop -> 42
stack: []
pop -> empty stack
* */
}

package three;import java.util.*;public class myHashTable {
public static void main(String args[]) {
// Create a hash map
Hashtable balance = new Hashtable();
Enumeration names;
String str;
double bal; balance.put("Zara", new Double(3434.34));
balance.put("Mahnaz", new Double(123.22));
balance.put("Ayan", new Double(1378.00));
balance.put("Daisy", new Double(99.22));
balance.put("Qadir", new Double(-19.08)); // Show all balances in hash table.
names = balance.keys();
while(names.hasMoreElements()) {
str = (String) names.nextElement();
System.out.println(str + ": " +
balance.get(str));
}
System.out.println();
// Deposit 1,000 into Zara's account
bal = ((Double)balance.get("Zara")).doubleValue();
balance.put("Zara", new Double(bal+1000));
System.out.println("Zara's new balance: " +
balance.get("Zara"));
} /*输出结果
Qadir: -19.08
Zara: 3434.34
Mahnaz: 123.22
Daisy: 99.22
Ayan: 1378.0 Zara's new balance: 4434.34
* */
}

package three;import java.util.*;public class myProperties {
public static void main(String args[]) {
Properties capitals = new Properties();
Set states;
String str; capitals.put("Illinois", "Springfield");
capitals.put("Missouri", "Jefferson City");
capitals.put("Washington", "Olympia");
capitals.put("California", "Sacramento");
capitals.put("Indiana", "Indianapolis"); // Show all states and capitals in hashtable.
states = capitals.keySet(); // get set-view of keys
Iterator itr = states.iterator();
while(itr.hasNext()) {
str = (String) itr.next();
System.out.println("The capital of " +
str + " is " + capitals.getProperty(str) + ".");
}
System.out.println(); // look for state not in list -- specify default
str = capitals.getProperty("Florida", "Not Found");
System.out.println("The capital of Florida is "
+ str + ".");
} /*输出结果
* The capital of Missouri is Jefferson City.
The capital of Illinois is Springfield.
The capital of Indiana is Indianapolis.
The capital of California is Sacramento.
The capital of Washington is Olympia. The capital of Florida is Not Found.
* */
}

public class GenericMethodTest
{
// 泛型方法 printArray
public static < E > void printArray( E[] inputArray )
{
// 输出数组元素
for ( E element : inputArray ){
System.out.printf( "%s ", element );
}
System.out.println();
} public static void main( String args[] )
{
// 创建不同类型数组： Integer, Double 和 Character
Integer[] intArray = { 1, 2, 3, 4, 5 };
Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };
Character[] charArray = { 'H', 'E', 'L', 'L', 'O' }; System.out.println( "整型数组元素为:" );
printArray( intArray ); // 传递一个整型数组 System.out.println( "\n双精度型数组元素为:" );
printArray( doubleArray ); // 传递一个双精度型数组 System.out.println( "\n字符型数组元素为:" );
printArray( charArray ); // 传递一个字符型数组
}
}/*输出结果
整型数组元素为:
1 2 3 4 5 双精度型数组元素为:
1.1 2.2 3.3 4.4 字符型数组元素为:
H E L L O
* */

public class MaximumTest
{
// 比较三个值并返回最大值
public static <T extends Comparable<T>> T maximum(T x, T y, T z)
{
T max = x; // 假设x是初始最大值
if ( y.compareTo( max ) > 0 ){
max = y; //y 更大
}
if ( z.compareTo( max ) > 0 ){
max = z; // 现在 z 更大
}
return max; // 返回最大对象
}
public static void main( String args[] )
{
System.out.printf( "%d, %d 和 %d 中最大的数为 %d\n\n",
3, 4, 5, maximum( 3, 4, 5 ) ); System.out.printf( "%.1f, %.1f 和 %.1f 中最大的数为 %.1f\n\n",
6.6, 8.8, 7.7, maximum( 6.6, 8.8, 7.7 ) ); System.out.printf( "%s, %s 和 %s 中最大的数为 %s\n","pear",
"apple", "orange", maximum( "pear", "apple", "orange" ) );
}
}/*输出结果
3, 4 和 5 中最大的数为 56.6, 8.8 和 7.7 中最大的数为 8.8pear, apple 和 orange 中最大的数为 pear
*/

public class Box<T> { private T t; public void add(T t) {
this.t = t;
} public T get() {
return t;
} public static void main(String[] args) {
Box<Integer> integerBox = new Box<Integer>();
Box<String> stringBox = new Box<String>(); integerBox.add(new Integer(10));
stringBox.add(new String("嗨..")); System.out.printf("整型值为 :%d\n\n", integerBox.get());
System.out.printf("字符串为 :%s\n", stringBox.get());
}
}
/*
整型值为 :10字符串为 :嗨..
*/

package three;import java.util.ArrayList;
import java.util.List;public class GenericTest {
public static void main(String[] args) {
List<String> name = new ArrayList<String>();
List<Integer> age = new ArrayList<Integer>();
List<Number> number = new ArrayList<Number>(); name.add("nick");
age.add(18);
number.add(530); getData(name);
getData(age);
getData(number);// getUperNumber(name); //报错
getUperNumber(age);
getUperNumber(number);
} public static void getData(List<?> data) {
System.out.println("getData :" + data.get(0));
} public static void getUperNumber(List<? extends Number> data) {
System.out.println("getUperNumber :" + data.get(0));
}
}/*输出结果
* getData :nick
getData :18
getData :530
getUperNumber :18
getUperNumber :530
* */