java--集合输出

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集合输出有四种方式:Iterator,ListIterator,foreach,Enumeration,

集合就用Iterator

public class test {    public static void main(String args[]) throws Exception {        Set<String> all = new HashSet<String>();        all.add("A");        all.add("B");        all.add("B");        Iterator<String> iter = all.iterator();        while(iter.hasNext()){            String str = iter.next();            System.out.println(str);        }    }}

ListIterator专门为List定义的双向迭代

public class test {    public static void main(String args[]) throws Exception {        List<String> all = new ArrayList<>();        all.add("A");        all.add("B");        all.add("B");        ListIterator<String> iter = all.listIterator();        System.out.print("由前向后输出:");        while(iter.hasNext()){            String str = iter.next();            System.out.print(str + ',');        }        System.out.print("\n由后向前输出:");        while(iter.hasPrevious()){            System.out.print(iter.previous() + ',');        }    }}

Enumeration适用于Vector
public boolean hasMoreElements(); //判断是否有下一个元素等同于hasNext()
public E nextElement();//取出下一个元素等同于next()

public class test {    public static void main(String args[]) throws Exception {        Vector<String> all = new Vector<>();        all.add("A");        all.add("B");        all.add("B");        Enumeration<String> iter = all.elements();        while(iter.hasMoreElements()){            System.out.println(iter.nextElement());        }    }}

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