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每天学Java-22 容器
2009-02-02 20:48
Java语言: 容器练习
import java.util.*;//要加上他。。
public class TestCollection {//容器练习 public static void main(String[] args){ Collection c= new ArrayList();//可以放入不同类型的对象 用父类的对象指向子类 面向对象的思想 c.add("hello"); c.add(new Name("f1","l1")); c.add(new Integer(100));//加入的是对象的引用 不能是基础类型，因为基础类型放在栈区，随时都有可能清空 System.out.println(c.size()); System.out.println(c); } } class Name{ Name(String s1,String s2){ } } /*结果: 3 [hello, Name@107077e, 100] */ Java语言: 练习遍历容器 Iterator
import java.util.*;//要加上他。。
public class TestCollection {//练习遍历容器 Iterator public static void main(String[] args){ Collection c= new ArrayList();//可以放入不同类型的对象 用父类的对象指向子类 面向对象的思想 c.add(new Name("f1","l1")); c.add(new Name("f2","l2")); c.add(new Name("f3","l3")); Iterator i = c.iterator(); while(i.hasNext()){//遍历 Name n =(Name)i.next(); System.out.println(n.getFistName()); } System.out.println(c.size()); System.out.println(c); } } class Name{ private String FirstName; private String SecondName; Name(String s1,String s2){ this.FirstName=s1;this.SecondName=s2; } public String toString(){ return FirstName+" "+SecondName; } public String getFistName(){ return FirstName; } } /*结果: f1 f2 f3 3 [f1 l1, f2 l2, f3 l3] */ Java语言: list练习
import java.util.*;
public class TestList { public static void main(String[] args){ List l1=new LinkedList(); for(int i=0;i<=5;i++){ l1.add("a"+i); } System.out.println(l1); l1.add(3,"a6"); System.out.println(l1); l1.set(6,"a7"); System.out.println(l1); System.out.println((String)l1.get(2)+" "); System.out.println(l1.indexOf("a3")); l1.remove(1); System.out.println(l1); Collections.shuffle(l1);//随机排列 System.out.println(l1); Collections.reverse(l1);//逆序 System.out.println(l1); Collections.sort(l1); System.out.println(l1);//排序 System.out.println(Collections.binarySearch(l1, "a3"));//折半法查找 } } /* 结果: [a0, a1, a2, a3, a4, a5] [a0, a1, a2, a6, a3, a4, a5] [a0, a1, a2, a6, a3, a4, a7] a2 4 [a0, a2, a6, a3, a4, a7] [a3, a2, a7, a6, a4, a0] [a0, a4, a6, a7, a2, a3] [a0, a2, a3, a4, a6, a7] 2 */ Java语言: map练习
import java.util.*;
public class Testmap { public static void main(String[] args) { Map m1=new HashMap(); Map m2= new HashMap(); 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(); System.out.println(i); } Map m3=new HashMap(m1); m3.putAll(m2); System.out.println(m3); } } /* 结果： 3 true true 2 {one=1, A=1, two=2, three=3, B=2} */ Java语言: map练习2
import java.util.*;
public class TestArgsWords { private static final Integer ONE =new Integer(1); //private static final int ONE = 1; public static void main(String[] args) { Map m =new HashMap(); for(int i=0;i<args.length;i++){ Integer freq = (Integer)m.get(args[i]); //int freq=(Integer)m.get(args[i])==null?0:(Integer)m.get(args[i]); m.put(args[i],(freq==null?ONE:new Integer(freq.intValue()+1))); } System.out.println(m.size()+"distinct words detected"); System.out.println(m); } } /* 4distinct words detected {a=2, aa=2, c=3, b=2} */ |
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