Java SE-容器/集合

/** *容器的学习 *学习Collection接口，其子接口：Set和List *实现Set接口的类：HashSet *实现List接口的类：LinkedList和ArrayList * *@study-jarek * */

import java.util.*;//javaSDk所提供的容器API位于java.util中
public class TestCollection2 { public static void main(String args[]) { //HashSet类(存储的数据无顺序，且不重复)
        Collection c1 = new HashSet(); c1.add("sun java");//添加的参数为Object类型
        c1.add(new Integer(100)); c1.add(new Person("jarek", 23)); System.out.println(c1); c1.remove("sun java"); System.out.println(c1.remove(new Person("jarek", 23))); System.out.println(c1); //ArrayList类(存储的数据有顺序，可重复)
        Collection c2 = new ArrayList(); c2.add("java sun"); c2.add(new Integer(120)); c2.add(new Person("Miss", 19)); System.out.println(c2); c2.remove(new Integer(120));//Integer类中重写了equals方法
        /* 自定义的类型，需要重写equals和hashCode方法 以实现自定义对象相等的规则 */ System.out.println(c2.remove(new Person("Miss", 19)));//若Person类未重写equals方法，则打印false
 System.out.println(c2); } } class Person { private String name; private int age; Person(String name, int age) { this.name = name; this.age = age; } public void setName(String name) { this.name = name; } public void setAge(int age) { this.age = age; } public String getName() { return name; } public int getAge() { return age; } public String toString() { return "姓名："+name+"—"+age; } //重写equals方法和hashCode方法
    public boolean equals(Object obj) { if(obj instanceof Person) { Person p = (Person)obj; Integer a = new Integer(p.age); Integer b = new Integer(age); return (name.equals(p.name)) &&(b.equals(a)); } return super.equals(obj); } public int hashCode() { return name.hashCode(); } }

/** *Iterator Interface *所有实现了Collection接口的容器都有一个Iterator方法 *用来返回一个实现了Iterator接口的对象 *Iterator对象称作迭代器，用来方便的实现对容器内元素的遍历 * *@study-jarek * */
import java.util.*; public class TestIterator { public static void main(String args[]) { Collection c = new HashSet(); c.add(new Family("jarek", 23, 361)); c.add(new Family("jelly", 21, 134)); c.add(new Family("storm", 22, 888)); c.add(new Family("casdffg", 22, 1231)); c.add(new Family("adadadaf", 43, 1434)); Iterator i = c.iterator(); while(i.hasNext()) { //next()的返回值是Object类型，需要转换为相应类型
            Family f = (Family)i.next(); System.out.print(f.getName()+" "); } for( Iterator a = c.iterator(); a.hasNext();) { Family f1 = (Family)a.next(); if(f1.getName().length()<6) { a.remove(); //c.remove(name);出错，不能用原来容器自身的remove方法，Iterator循环内部，执行了锁定，锁定当前元素。
 } } System.out.println(c); } } class Family { private String name; private int age; private int id; Family(String name, int age, int id) { this.name = name; this.age = age; this.id = id; } public void setName(String name) { this.name = name; } public void setAge(int age) { this.age = age; } public void setId(int id) { this.id = id; } public String getName() { return name; } public int getAge() { return age; } public int getId() { return id; } public String toString() { return name+"_"+age+"_"+id; } }

/** *增强的for循环 *对于遍历array和Collection的时候相当简便 *数组：缺陷，不能方便的访问下标值 *集合：与使用Iterator相比，不能方便的删除集合中的内容 *在内部也是调用Iterator *除了简单的遍历并读出其中的内容外，不建议使用 * *@study-jarek * */
import java.util.*; public class TestEnhanceFor { public static void main(String args[]) { int[] arr = { 1, 2, 3, 4, 5, 6}; for( int i : arr ) { System.out.print(i+" "); } System.out.println(); Collection c = new ArrayList(); c.add("aaa"); c.add("bbb"); c.add("ccc"); for( Object o : c ) { System.out.println(o); } } }