Java 编程思想（第4版）学习笔记（迭代器 Iterator ListIterator 第11章练习11）

package Exer_11;

import java.util.Iterator;

import java.util.Vector;

/**

* @author lzcysd

*

*/

public class InteratorTest {

/**

* @param args

*/

public static void main(String[] args) {

String[] num = {"one","two","three","four","five","six","seven","eight","nine","ten"};

Vector<String> aVector = new Vector<String>(java.util.Arrays.asList(num));

//Vector是同步的，线程安全。ArrayList是非同步的，效率高

System.out.println("Before Vector: " + aVector);

Iterator <String> nums = aVector.iterator();

//iterator方法将返回一个Iterator

while(nums.hasNext()){ //检查序列中是否还有元素

String aString = nums.next(); //next获得序列中是否还有元素

System.out.println(aString);

if(aString.length() > 4) //去除大于4个单词的词语

nums.remove();

//remove()将去除集合（不是Interator类）中最后调用next()返回的元素

}

System.out.println("After Vector: " + aVector);

}

}

/* Before Vector: [one, two, three, four, five, six, seven, eight, nine, ten]

* one

* two

* three

* four

* five

* six

* seven

* eight

* nine

* ten

* After Vector: [one, two, four, five, six, nine, ten]

*/

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package Exer_11;

/*

* 写一个方法，使用Iterator遍历Collection，并打印容器中每个对象的toString()

* 填充各种类型的Collection，然后对其使用此方法

*/

import java.util.*;

import static java.lang.System.out;

public class Exer_11_11 {

public static void printAny(Collection c){

Iterator it = c.iterator();

while(it.hasNext())

out.print(it.next() + "");

out.println();

}

public static void main(String[] args){

ArrayList<Integer> al =

new ArrayList<Integer>(Arrays.asList(1, 2, 3 ));

LinkedList<Character> ll =

new LinkedList<Character>(Arrays.asList('a', 'b', 'c'));

HashSet<Float> hs =

new HashSet<Float>(Arrays.asList(1.1f, 2.2f, 3.3f));

TreeSet<Double> ts =

new TreeSet<Double>(Arrays.asList(1.11, 2.22, 3.33));

LinkedHashSet<Integer> lhs =

new LinkedHashSet<Integer>(Arrays.asList(11, 22, 33));

printAny(al);

printAny(ll);

printAny(hs);

printAny(ts);

printAny(lhs);

}

}

/*

* 123

* abc

* 1.12.23.3

* 1.112.223.33

* 112233

*/

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package Exer_11;

import java.util.*;

/**

* ListIterator是一个更强大的Iterator的子类型，他只能用于List类

* 可以双向移动，可以使用set()方法替换它访问过的最后一个元素

* 还可以调用listIterator(n)方法创建一个一开始就指向索引为n的元素处ListIterator

* @author lzcysd

*

*/

public class ListIteratiorTest {

/**

* @param args

*/

public static void main(String[] args) {

List<String> aList = new ArrayList<String>(Arrays.asList("aaa","bbb","ccc","ddd","eee","fff","ggg","hhh"));

ListIterator<String> it = aList.listIterator();

while(it.hasNext())

System.out.print(it.next() + ", " + it.nextIndex() +

", " + it.previousIndex() + ";" );

System.out.println();

while(it.hasPrevious())

System.out.print(it.previous() + " ");

System.out.println();

System.out.println(aList);

it = aList.listIterator(3); //it的第一个元素为aList第4个元素

while(it.hasNext()){

String stemp =it.next();

it.set("3" + stemp);

//相当于把aList从第4个元素（索引为3）开始的其他元素的内容前面都加上3

}

System.out.println(aList);

}

}

/** output

* aaa, 1, 0;bbb, 2, 1;ccc, 3, 2;ddd, 4, 3;eee, 5, 4;fff, 6, 5;ggg, 7, 6;hhh, 8, 7;

* hhh ggg fff eee ddd ccc bbb aaa

* [aaa, bbb, ccc, ddd, eee, fff, ggg, hhh]

* [aaa, bbb, ccc, 3ddd, 3eee, 3fff, 3ggg, 3hhh]

*/