文章目錄
集合框架
1.size()
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
System.out.println(c.size()); //查看當前集合中所有的元素
}
}
2.add(Object a) | addAll(Collection c)
//向集合中添加元素
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class PersonDemo1 {
private String name;
private int age;
//添加get|set方法快捷鍵 ALT+SHIFT+S+R
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
//添加有參構造函數 快捷鍵 ALT+SHIFT+S+O
public PersonDemo1(String name, int age) {
super();
this.name = name;
this.age = age;
}
//添加構造函數 快捷鍵 ALT+SHIFT+S+C
public PersonDemo1() {
super();
// TODO Auto-generated constructor stub
}
}
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(123); //自動裝箱
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.addAll(c); //添加另一個集合中的所有元素
c1.add("bb");
System.out.println(c1.size());
System.out.println(c1); //輸出集合中的所有元素
}
}
3.clear()
//清空當前集合
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(123); //自動裝箱
Collection c1=new ArrayList();
c1.addAll(c);
c1.add("bb");
c1.clear();
System.out.println(c1.size());
}
}
4.isEmpty()
//判斷當前集合是否爲空
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(123); //自動裝箱
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.addAll(c);
c1.add("bb");
c1.clear(); //清空集合中所有元素
System.out.println(c1.isEmpty());
}
}
5.remove(Object o)
//刪除集合中某個元素
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(123); //自動裝箱
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.addAll(c);
c1.add("bb");
System.out.println(c1);
c1.remove("bb");
System.out.println(c1);
}
}
6.removeAll(Collection c)
//刪除集合中某個集合
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(123); //自動裝箱
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.addAll(c);
c1.add("bb");
System.out.println(c1);
c1.removeAll(c);
System.out.println(c1);
}
}
7.contains(Object o)
//判斷是否包含某個元素
/*判斷依據：
根據元素所在類中的equals方法來進行判斷的
注意：如果是自定義類 要求重寫equals方法
*/
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
package chapter09;
public class PersonDemo1 {
private String name;
private int age;
//添加get|set方法快捷鍵 ALT+SHIFT+S+R
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
//添加有參構造函數 快捷鍵 ALT+SHIFT+S+O
public PersonDemo1(String name, int age) {
super();
this.name = name;
this.age = age;
}
//添加構造函數 快捷鍵 ALT+SHIFT+S+C
public PersonDemo1() {
super();
// TODO Auto-generated constructor stub
}
//重寫equals方法 快捷鍵 ALT+SHIFT+S+V
@Override
public boolean equals(Object obj) {
// TODO Auto-generated method stub
PersonDemo1 p =(PersonDemo1) obj;
if((this.name==p.name)&&(this.age==p.age))
{
return true;
}
else
return false;
}
}
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
boolean flag=c.contains(new PersonDemo1("張三",20)); //重寫了equals方法
System.out.println(flag);
}
}
8.containsAll(Collection c)
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.add("aa");
System.out.println(c1.containsAll(c));
}
}
9.equals(Collection o)
//比較兩個集合中的所有元素是否相等
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add(new PersonDemo1("張三",20));
c.add(new PersonDemo1("李四",19));
Collection c1=new ArrayList();
c1.add("aa");
System.out.println(c1.equals(c));
}
}
10.returnAll
//求兩個集合的交集，並返還給原集合
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add("aa");
c.add(123);
Collection c1=new ArrayList();
c1.add("aa");
c1.add("bb");
c1.add(234);
c.retainAll(c1);
System.out.println(c);
}
}
11.toArray()
//將Object類轉換成數組
package chapter09;
import java.util.ArrayList;
import java.util.Collection;
public class CollectionDemo1 {
public static void main(String[] args)
{
CollectionDemo1 c=new CollectionDemo1();
c.CollectionTest();
}
public void CollectionTest()
{
Collection c=new ArrayList();
c.add("aa");
c.add(123);
Collection c1=new ArrayList();
c1.add("aa");
c1.add("bb");
c1.add(234);
Object[] o=c.toArray();
for(int i=0;i<c.size();i++)
System.out.println(o[i]);
}
}
