存放在java.util.*
。是一个存放对象的容器。
collection的使用
增加元素 add();
判断是否包含某个元素 contains();
删除某个元素 remove();
遍历元素(iterator迭代器)
package com.zheng.demo1;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class MyCollection {
public static void main(String[] args) {
Collection c = new ArrayList();
//增加元素
c.add("足球");
c.add("篮球球");
c.add("乒乓球");
//集合大小
System.out.println("当前集合大小:" + c.size());
//判断是否包含某个元素
System.out.println(c.contains("足球"));
//删除元素
c.remove("足球");
System.out.println("删除一个元素之后大小:" + c.size());
System.out.println("===============");
//打印,增强for循环
for (Object obj : c) {
System.out.println("增强for循环取值:"+obj);
}
System.out.println("==============");//迭代器形式
Iterator it = c.iterator();
while (it.hasNext()){//判断有无下一个元素
Object obj=it.next();//取值
System.out.println("iterator取值:"+obj);
}
}
}
Iterator:迭代器
在JAVA中,所有的对象都有toString方法;方便打印
通过添加一个对象到collection集合中
实体类
package com.zheng.demo1;
public class Student {
private int id;
private String name;
private String address;
public Student() {
}
public Student(int id, String name, String address) {
this.id = id;
this.name = name;
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
}
加入到集合
package com.zheng.demo1;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class MyCollection1 {
public static void main(String[] args) {
//创建容器
Collection<Student> students = new ArrayList<Student>();
//创建对象
Student student1 = new Student(1, "小明", "北京");
Student student2 = new Student(2, "小红", "河南");
Student student3 = new Student(3, "小黑", "深圳");
Student student4 = new Student(4, "小蓝", "上海");
//添加对象到容器中
students.add(student1);
students.add(student2);
students.add(student3);
students.add(student4);
//查看
System.out.println(students.toString());
System.out.println("=========增强for循环输出=========");
//增强for循环输出
for (Student student : students) {
System.out.println(student.toString());
}
System.out.println("=========迭代器输出=========");
//迭代器输出
Iterator<Student> iterator = students.iterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
}
}
}
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