155_集合_Collection集合的常用方法详解_03_contains

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import java.util.ArrayList;import java.util.Collection;public class ContainsTest {public static void main(String[] args) {//建立集合Collection  C = new ArrayList();//添加元素C.add(1);//判断是否包含System.out.println(C.contains(1));//trueInteger m = new Integer(50);C.add(m);Integer n = new Integer(50);//System.out.println(C.contains(n));//true 说明底层已经重写了equals方法Manager m1 = new Manager(100, "jack");C.add(m1);Manager m2 = new Manager(100, "jack");//如果两个引用的编号和姓名一致，那说明包含，这样把底层的equals方法进行重写//而contains在底层的时间使用equals方法判断是否重复System.out.println(C.contains(m2));//**********************************************contains(Object o)在ArrayList中的实现方法// public boolean contains(Object o) {//        return indexOf(o) >= 0;//    }////    /**//     * Returns the index of the first occurrence of the specified element//     * in this list, or -1 if this list does not contain the element.//     * More formally, returns the lowest index <tt>i</tt> such that//     * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,//     * or -1 if there is no such index.//     *///    public int indexOf(Object o) {//        if (o == null) {//            for (int i = 0; i < size; i++)//                if (elementData[i]==null)//                    return i;//        } else {//            for (int i = 0; i < size; i++)//                if (o.equals(elementData[i]))//                    return i;//        }//        return -1;//    }}}class Manager{     int number;     String name;     public Manager(int number,String name) {this.number=number;this.name=name;}     public boolean equals(Object o){     if(this==o)     return true;     if (o instanceof Manager){     Manager s =(Manager)o;     if(s.number==this.number && s.name.equals(this.name)){     return true;     }     }     return false;     }}
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