概述
Enumeration：
| import java.util.Vector; import java.util.Enumeration;
public static void enumerationDemo() { Vector<String> fruits = new Vector<String>(); fruits.add("Apple"); fruits.add("Banana"); fruits.add("Pear"); fruits.add("Pinapple"); Enumeration<String> fruitEnum = fruits.elements(); while (fruitEnum.hasMoreElements()) { System.out.println(fruitEnum.nextElement()); } }
// 输出 // Apple // Banana // Pear // Pinapple |
BitSet：
| import java.util.BitSet; public static void bitSetDemo() { BitSet bs1 = new BitSet(16); BitSet bs2 = new BitSet(16); for (int i = 0; i < 16; i+=2) { bs1.set(i); // set to true bs2.set(i+1, true); // also set to true } System.out.println(bs1); //bs1:1010 1010 1010 1010 System.out.println(bs2); //bs2:0101 0101 0101 0101
BitSet bs3 = new BitSet(16); //bs3:1111 1111 1111 1111 bs3.set(0, 8); bs3.set(8, 16, true); System.out.println(bs3);
// 'not' bs1 = !(1010 1010 1010 1010) = 0101 0101 0101 0101, // bs3 'and' ('not' bs1) = 0101 0101 0101 0101 & 1111 1111 1111 1111 // = 0101 0101 0101 0101 bs3.andNot(bs1); System.out.println(bs3);
// cardinality returns how many 'true' were set in the bitset, here we got 8 System.out.println(bs3.cardinality());
bs1.and(bs2); //bs1:0000 0000 0000 0000 System.out.println(bs1);
bs1.set(8, 16, true); //bs1:0000 0000 1111 1111 System.out.println(bs1);
bs1.clear(13); //bs1:0000 0000 1111 1011 System.out.println(bs1);
bs3 = (BitSet)bs1.clone(); //bs3:0000 0000 1111 1011 bs1.clear(8, 12); //bs1:0000 0000 0000 1011 System.out.println(bs1); System.out.println(bs3); bs1.clear(); //bs1:0000 0000 0000 0000
System.out.println(bs1.equals(bs3)); bs1.flip(1, 15); //bs1:0111 1111 1111 1110 System.out.println(bs1); bs1.flip(10); //bs1:0111 1111 1101 1110
System.out.println(bs1.get(10));
bs1.xor(bs3); //bs1:0111 1111 0010 0101 System.out.println(bs1);
BitSet bs4 = bs1.get(4, 12); //bs4:1111 1101 System.out.println(bs4); System.out.println(bs4.hashCode()); // get hash code for this set
BitSet bs5 = new BitSet(8); bs5.set(0, 4); //bs5:1111 0000 BitSet bs6 = new BitSet(8); bs6.set(4, 8); //bs6:0000 1111 // bs5 and bs6 don't have a same bit that is set to 'true', // intersects will return false System.out.println(bs5.intersects(bs6)); bs6.set(2); //bs6:0010 1111 // bs5 and bs6 intersects at bit '2' System.out.println(bs5.intersects(bs6));
// nextClearBit returns the index of the first bit // that is set to false starting from the specified index System.out.println(bs5.nextClearBit(0)); // nextClearBit returns the index of the first bit // that is set to true starting from the specified index System.out.println(bs6.nextSetBit(0));
bs5.or(bs6); //bs5:1111 1111 System.out.println(bs5);
BitSet bs7 = new BitSet(16); //size returns the number of bits os space actually in use by this set System.out.println(bs7.size()); //length returns the "logic size": the index of the highest set bit + 1 bs7.set(9); System.out.println(bs7.length()); } |
FixedArray &ArrayList：
| import java.util.ArrayList; import java.util.Set; import java.util.HashSet;
public static void arrayDemo() { // fix-sized array ============================================= int[] arr1 = new int[10]; String[] arr2 = {"a", "b", "c", "d", "e"}; String[] arr3 = new String[]{"a", "b", "c"};
System.out.println(Arrays.toString(arr1)); //output: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] System.out.println(Arrays.toString(arr2)); //output: [a, b, c, d, e]
ArrayList<String> arrList = new ArrayList<String>(Arrays.asList(arr2)); System.out.println(arrList); //output: [a, b, c, d, e]
String[] arr4 = new String[arrList.size()]; arrList.toArray(arr4); System.out.println(Arrays.toString(arr4)); //output: [a, b, c, d, e]
Set<String> set = new HashSet<String>(Arrays.asList(arr4)); System.out.println(set); //output: [a, b, c, d, e]
//dynamic array list ============================================= ArrayList<Integer> list1 = new ArrayList<Integer>(); ArrayList<Integer> list2 = new ArrayList<Integer>(10); for (int i = 0; i < 10; i++) { list2.add(i); } ArrayList<Integer> list3 = new ArrayList<Integer>(list2); System.out.println(list3); //output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
System.out.println(list1.isEmpty()); //output: true
list1.addAll(list3); System.out.println(list1); //output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] list1.addAll(5, list3); System.out.println(list1); //output: [0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 5, 6, 7, 8, 9]
System.out.println(list1.containsAll(list2)); //output: true list2.add(10); System.out.println(list1.containsAll(list2)); //output: false
System.out.println(list1.indexOf(4)); //output: 4 System.out.println(list1.lastIndexOf(4)); //output: 9
System.out.println(list1.size()); //output: 20
System.out.println(list1.subList(4, 10)); //output: [4, 0, 1, 2, 3, 4]
ArrayList<Integer> list4 = (ArrayList<Integer>)list1.clone(); list1.clear(); } |
Vector：
| import java.util.Vector; import java.util.List;
public static void vectorDemo() { //constructors Vector<String> vec1 = new Vector<String>(); Vector<String> vec2 = new Vector<String>(10); Vector<String> vec3 = new Vector<String>(10, 3); String[] arr1 = {"a", "b", "c", "d", "e"}; Vector<String> vec4 = new Vector<String>(Arrays.asList(arr1));
//add methods for (int i = 0; i < 10; i++) { vec1.add(String.format("%d", i)); } //vec1: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] vec2.addAll(vec4); //vec2: [a, b, c, d, e] vec2.addAll(3, vec1); //vec2: [a, b, c, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, d, e] vec2.add(8, "test"); //vec2: [a, b, c, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9, d, e] vec2.addElement("abc"); //vec2: [a, b, c, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9, d, e, abc] vec2.insertElementAt("def", 3); //vec2: [a, b, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9, d, e, abc]
//get methods Enumeration<String> iter = vec2.elements(); while(iter.hasMoreElements()) { System.out.println(iter.nextElement()); } String strAtPos3 = vec2.get(3); //position starts at index 0 String strAtPos3_1 = vec2.elementAt(3); //position starts at index 0 String firstStr = vec2.firstElement(); //a String lastStr = vec2.lastElement(); //abc
//Vector basic methods System.out.println(vec2.capacity()); //20, capacity is pre-allocated size System.out.println(vec2.size()); //18, size is the number of elements System.out.println(vec2.isEmpty()); //false //if newSize is greater than current size, null elements will be appended, //if newSize is less than current size, all elements after index "newSize" //will be discarded vec2.setSize(15); //vec2: [a, b, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9] vec2.trimToSize(); //trim empty positions, capacity will be equal to size //enlarge capacity, at lease the capacity should hold the size vec2.ensureCapacity(10); //capacity should be 15 now Vector<String> vecNew = (Vector<String>)vec2.clone(); System.out.println(vec2.hashCode()); System.out.println(vecNew.equals(vec2));
//index and contain methods System.out.println(vec2.indexOf("test")); //9 (index starts at 0) System.out.println(vec2.indexOf("1", 8)); //-1 (Searching starts at index 8) System.out.println(vec2.lastIndexOf("test")); //9 System.out.println(vec2.lastIndexOf("test", 6)); //-1 (Searching from index 6 to 0) System.out.println(vec2.contains("test")); System.out.println(vec2.containsAll(vec1)); //vec1: [0,1,2,3,4,5,6,7,8,9]
//set methods vec2.set(0, "Start"); //vec2: [Start, b, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9] vec2.setElementAt("SecElem", 1); //vec2: [Start, SecElem, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9] System.out.println(vec2);
//remove methods vecNew.remove(10); //vecNew: [a, b, c, def, 0, 1, 2, 3, 4, test, 6, 7, 8, 9] //remove the first match element vecNew.remove("2"); //vecNew: [a, b, c, def, 0, 1, 3, 4, test, 6, 7, 8, 9] vecNew.removeAll(vec4); //vecNew: [def, 0, 1, 3, 4, test, 6, 7, 8, 9] vecNew.removeElementAt(2); //vecNew: [def, 0, 3, 4, test, 6, 7, 8, 9] vecNew.removeElement("4"); //vecNew: [def, 0, 3, test, 6, 7, 8, 9] //remove all elements that are not contained in the param collection vecNew.retainAll(vec1); //vecNew: [0, 3, 6, 7, 8, 9] vecNew.removeAllElements(); //size will be 0, capacity will remain vecNew.clear(); //similar to removeAllElements System.out.println(vecNew);
//convert methods String[] sArr = new String[vec2.size()]; vec2.copyInto(sArr); //sArr: [Start, SecElem, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9] List l = vec2.subList(6, 10); //l: [2, 3, 4, test] Object[] ol1 = vec2.toArray(); for (int i = 0; i < ol1.length; i++) { System.out.println(ol1[i]); } String[] targetArr = new String[vec2.size()]; vec2.<String>toArray(targetArr); //targetArr: [Start, SecElem, c, def, 0, 1, 2, 3, 4, test, 5, 6, 7, 8, 9] System.out.println(vec2.toString()); } |
Stack：
Stack继承自Vector，所以Stack继承了Vector中定义的全部方法，除了Vector中的方法，Stack还定义了一些自己特有的方法
| import java.util.Stack;
public static void stackDemo() { //Stack is derived from Vector Stack<Integer> s1 = new Stack<Integer>(); for (int i = 0; i < 10; i+=2) { s1.push(i); } System.out.println(s1); //[0, 2, 4, 6, 8] System.out.println(s1.peek()); //8 Integer top = s1.pop(); System.out.println(top); //8 System.out.println(s1.peek()); //6 System.out.println(s1.search(2)); //3 System.out.println(s1.search(3)); //-1 } |
Dictionary：
Dictionary是抽象类，不能实例化，Hashtable就是一个Dictionary的实现类，不过Dictionary已经过时，目前通常使用Map接口，Hashtable也实现了Map接口的方法
Hashtable：
| import java.util.Hashtable;
public static void hashtableDemo() { Hashtable<String, Integer> ht1 = new Hashtable<String, Integer>(); for (int i = 0; i < 10; i++) { ht1.put(String.format("Test%d", i), i); } Hashtable<String, Integer> ht2 = (Hashtable<String, Integer>)ht1.clone(); Hashtable<String, Integer> ht3 = new Hashtable<String, Integer>(10, 0.8f);
System.out.println(ht3.isEmpty()); //true System.out.println(ht2.size()); //10
Enumeration<Integer> values = ht2.elements(); while (values.hasMoreElements()) { System.out.println(values.nextElement()); }
if (ht2.contains(5)) { // or use containsValue(5) Enumeration<String> keys = ht2.keys(); while (keys.hasMoreElements()) { String key = keys.nextElement(); Integer value = ht2.get(key); if (value == 5) { System.out.println(key); } } }
if (ht2.containsKey("Test2")) { System.out.println(ht2.get("Test2")); }
ht1.clear(); System.out.println(ht2); ht2.remove("Test5"); System.out.println(ht2); } |
Map：
| import java.util.Map; import java.util.HashMap; import java.util.Set; import java.util.Collection;
public static void hashmapDemo() { Map<Integer, String> m1 = new HashMap<Integer, String>(); for (int i = 0; i < 10; i++) { m1.put(i, String.format("Test%d", i)); } System.out.println(m1);
Set<Map.Entry<Integer, String>> set = m1.entrySet(); for (Map.Entry<Integer, String> entry : set) { System.out.println(entry.getKey() + ":" + entry.getValue()); }
System.out.println(m1.containsKey(4)); System.out.println(m1.containsValue("Test5"));
Set<Integer> keys = m1.keySet(); Collection<String> values = m1.values(); m1.remove(6);
System.out.println(keys); System.out.println(values); } |
Set：
Set不包含重复元素
| import java.util.ArrayList; import java.util.Set;
public static void setDemo() { int[] nums = new int[] {1, 4, 8, 3, 22, 34, 4, 6, 0, 33, 5, 6, 3, 9}; List list = new ArrayList(); for (int i:nums) { list.add(i); } System.out.println(list); //[1, 4, 8, 3, 22, 34, 4, 6, 0, 33, 5, 6, 3, 9] Set<Integer> set = new HashSet<Integer>();
//remove duplicate elements set.addAll(list); System.out.println(set); //[0, 1, 33, 34, 3, 4, 5, 22, 6, 8, 9] set.add(4); //4 is a duplicate element, so this will not take effect System.out.println(set); //[0, 1, 33, 34, 3, 4, 5, 22, 6, 8, 9]
System.out.println(set.size()); //11 } |
Properties：
Properties 继承于Hashtable.表示一个持久的属性集.属性列表中每个键及其对应值都是一个字符串
| import java.util.Properties;
public static void propertiesDemo() { Properties props = new Properties(); props.put("Key1", "Value1"); props.setProperty("Key2", "Value2"); props.list(System.out); //-- listing properties -- //Key2=Value2 //Key1=Value1 System.out.println(props.getProperty("Key1")); //Value1 } |
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