Collections工具类

1 操作Collection及Map工具类

package lianxi2;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.junit.Test;

public class TestCollections {
@Test
   public void test1(){
    List list = new ArrayList();
    list.add(3242);
    list.add(23);
    list.add(55);
    list.add(2233);
    list.add(90);
    System.out.println(list);
    System.out.println(Collections.max(list));
    Collections.reverse(list);
    System.out.println(list);
    Collections.swap(list, 3, 4);
    System.out.println(list);
    //copy()方法
    List list1 = Arrays.asList(new Object[list.size()]);
    Collections.copy(list1, list);
    System.out.println("list1="+list);
    //保证线程安全
    List list2 = Collections.synchronizedList(list);
    System.out.println("list2="+list2);
}
}

结果：

[3242, 23, 55, 2233, 90]

3242

[90, 2233, 55, 23, 3242]

[90, 2233, 55, 3242, 23]

list1=[90, 2233, 55, 3242, 23]

list2=[90, 2233, 55, 3242, 23]