java基础之ArrayList类去除重复元素

去除重复字符串

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public class List01 {    public static void main(String[] args) {        List<String> list = new ArrayList<String>();        list.add("张三");        list.add("李四");        list.add("王五");        list.add("赵六");        list.add("李四");        list.add("王五");        System.out.println("-----去除重复元素之前------");        Iterator<String> it = list.iterator();        while(it.hasNext()){            String str = it.next();            System.out.println(str);        }        //开始去除重复元素        //创建新的集合        List<String> newList = new ArrayList<String>();        //遍历旧集合        for(String str : list){            //如果旧集合中不包含指定元素，则添加到新集合中            if(!newList.contains(str))                newList.add(str);        }        System.out.println("-----去除重复元素之后------");        //遍历新集合        Iterator<String> newIt = newList.iterator();        while(newIt.hasNext()){            System.out.println(newIt.next());        }    }}

结果

-----去除重复元素之前------张三李四王五赵六李四王五-----去除重复元素之后------张三李四王五赵六

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去除重复对象

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class Book{    private String name;    private double price;    public Book() {    }    public Book(String name, double price) {        this.name = name;        this.price = price;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public double getPrice() {        return price;    }    public void setPrice(double price) {        this.price = price;    }    public boolean equals(Object obj) {        if(this==obj)            return true;        if(obj==null)            return false;        if(!(obj instanceof Book))            return false;        Book book = (Book)obj;        if(this.price != book.price)            return false;        if(this.name==null){            if(book.name!=null)                return false;        }else if(!this.name.equals(book.name))            return false;        return true;    }    @Override    public String toString() {        return "Book [name=" + name + ", price=" + price + "]";    }}public class List02 {    public static void main(String[] args) {        List<Book> list = new ArrayList<Book>();        Book b1 = new Book("java编程思想",89.8);        Book b2 = new Book("深入理解jvm",79.8);        Book b3 = new Book("算法导论",69.9);        Book b4 = new Book("面向对象程序设计",49.9);        Book b5 = new Book("java编程思想",89.8);        Book b6 = new Book("深入理解jvm",79.8);        Book b7 = new Book("算法导论",69.9);        Book b8 = new Book("面向对象程序设计",49.9);        list.add(b1);        list.add(b2);        list.add(b3);        list.add(b4);        list.add(b5);        list.add(b6);        list.add(b7);        list.add(b8);        List<Book> newList = new ArrayList<Book>();        Iterator<Book> it =list.iterator();        while(it.hasNext()){            Book book = it.next();            if(!newList.contains(book))                newList.add(book);        }        Iterator<Book> newIt = newList.iterator();        while(newIt.hasNext()){            System.out.println(newIt.next());        }    }}

结果

Book [name=深入理解jvm, price=79.8]Book [name=算法导论, price=69.9]Book [name=面向对象程序设计, price=49.9]Book [name=null, price=49.9]