System.out.print("3 是否在 arraylist: "); System.out.println(numbers.contains(3)); // 检查1是否在这个数组中 System.out.print("1 是否在 arraylist: "); System.out.println(numbers.contains(1)); } } 执行以上程序输出结果为: NumberArrayList:[2,3,5]3是否在arraylist:true1是否在arraylist:fal...
importjava.util.ArrayList;publicclassMain{publicstaticvoidmain(String[]args){ArrayList<String>cars=newArrayList<String>();cars.add("Volvo");cars.add("BMW");cars.add("Ford");cars.add("Mazda");System.out.println(cars.contains("BMW"));System.out.println(cars.contains("Toyota"));}} ...
Point1 b=newPoint1(1,2); list.add(a);if(list.contains(b)){ System.out.println("1"); } } } 无输出,因为对象a和b是拥有不同的引用! 看ArrayList的contains的源码 publicbooleancontains(Object o) {returnindexOf(o) >= 0; }publicintindexOf(Object o) {if(o ==null) {for(inti = 0; ...
时间上差很远，内存虽然差不多但是前者击败30%，后者击败94%。这两种解法区别是用一条ArrayList还是两条来存数据，所以contains虽然执行次数一样但是检测的长度上不一样，而且ArrayList的扩容次数也不一样，所以学习一下。contains(Object o)直接翻(JDK8)源码:null和object区分开来还是因为equals有一方是null的话都会导...
public boolean contains(Object o)The contains() method is used to determines whether an element exists in an ArrayList object. Returns true if this list contains the specified element. Package: java.utilJava Platform: Java SE 8 Syntax:contains(Object o)...
1)ArrayList的contains方法的简介: public boolean contains(Objecto) 如果此列表包含指定的元素o,则返回true。 2)重写equals方法以便使用自己的方式去对比集合中的两个对象是否相同: //重写equals方法publicbooleanequals(Object obj) {if(objinstanceofmyChar) {return((myChar)obj).getValue() ==this.value; ...
该方法可以去掉 ArrayList 占用的多余的空间或内存,因为 ArrayList 每次扩容后总会有所剩余,如果数组很大,占用的多余的空间会比较大,内存不够时可以使用此方法。 2)ensureCapacity 方法 public void ensureCapacity(int minCapacity) Increases the capacity of this ArrayList instance, if necessary, to ensure that it...
ArrayListis an ordered collection and it allows duplicate elements. It is widely used to store and retrieve data. We have seen a few methods of the ArrayList class before likeadd(),addAll(),remove(),set(),iterate()andclear(). Today we will see thecontains()method. ...
再回到contains方法中,如果indexOf返回的是-1,则返回false;如果返回的是个非负整数,则返回这个数,即找到的相同元素(字符串)的位置。 泛型为包装类时 import java.util.ArrayList; public class Test { public static void main(String[] args) { //包装类 ...
ArrayList 2 contains all elements of ArrayList 1: false In the above example, we have created two arraylists namedlanguages1andlanguages2. Notice the expression, // return truelanguages1.containsAll(languages2) Here, thecontainsAll()method checks iflanguages1contains all elements oflanguages2. Hence...