Collections操作实例

<1>实例操作一：返回不可变的集合

Collections类中可以返回空的List、Set、Map集合，但是通过这种方式返回的对象是无法进行增加数据的，因为在这些操作中并没有实现add()方法

import java.util.Collections;
import java.util.List;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		List<String> allList = Collections.emptyList();			//返回不可变的空List集合
		Set<String> allSet = Collections.emptySet();			//返回不可变的空List集合
	}

}

<2>实例操作二：为集合增加内容

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
	}

}

<3>实例操作三：反转集合中的内容

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		Collections.reverse(all);											//内容反转保存
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
	}

}

<4>实例操作四：检索内容

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		Collections.reverse(all);											//内容反转保存
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
		int point = Collections.binarySearch(all,"zhangsan");
		System.out.println("检索结果："+point); 			//输出位置
		
	}

}

<5>实例操作五：替换集合中的内容

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
//		List<String> allList = Collections.emptyList();			//返回不可变的空List集合
//		Set<String> allSet = Collections.emptySet();			//返回不可变的空List集合
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		
		Collections.replaceAll(all, "wangwu", "lisi");			//替换内容
		
		Collections.reverse(all);											//内容反转保存
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
		int point = Collections.binarySearch(all,"zhangsan");
		System.out.println("检索结果："+point); 			//输出位置
		
	}

}

<6>实例操作六：集合排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
//		List<String> allList = Collections.emptyList();			//返回不可变的空List集合
//		Set<String> allSet = Collections.emptySet();			//返回不可变的空List集合
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		
//		Collections.replaceAll(all, "wangwu", "lisi");			//替换内容
		
//		Collections.reverse(all);											//内容反转保存
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
		Collections.sort(all);
		System.out.println("排序之后的集合");
		iter = all.iterator();
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
		int point = Collections.binarySearch(all,"zhangsan");
		System.out.println("检索结果："+point); 			//输出位置
		
	}

}

<7>实例操作七：交换指定位置的内容

直接使用swap()方法可以把集合中两个位置的内容进行交换

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

//=================================================
// File Name       :	Collection_demo
//------------------------------------------------------------------------------
// Author          :	Common



//主类
//Function        : 	Collection_demo;
public class Collection_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
//		List<String> allList = Collections.emptyList();			//返回不可变的空List集合
//		Set<String> allSet = Collections.emptySet();			//返回不可变的空List集合
		
		List<String> all = new ArrayList<String>();			//实例化List
		Collections.addAll(all, "zhangsan","lisi","wangwu");		//增加内容
		
//		Collections.replaceAll(all, "wangwu", "lisi");			//替换内容
		
//		Collections.reverse(all);											//内容反转保存
		Iterator<String> iter = all.iterator();					//实例化iterator对象
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
//		Collections.sort(all);
		Collections.swap(all,0,2);		//交换指定位置的内容
		System.out.println("排序之后的集合");
		iter = all.iterator();
		while(iter.hasNext()){
		System.out.println(iter.next()+"、");
		}
		
		int point = Collections.binarySearch(all,"zhangsan");
		System.out.println("检索结果："+point); 			//输出位置
		
	}

}