Java.util.ArrayList.contains() Java.util.ArrayList.clone() Java.util.ArrayList.ensureCapacity() 描述 该java.util.ArrayList.contains(Object)如果此列表包含指定的元素,方法返回true。 声明 以下是java.util.ArrayList.contains()方法的声明 public boolean contains(Object o) 参数 o - 要测试其在此列表中的存在的元素。 返回值 如果此列表包含指定的元素,则此方法返回true。 异常 NA 实例 以下示例显示了java.util.Arraylist.contains方法的用法。 package com.tutorialspoint; import java.util.ArrayList; public class ArrayListDemo { public static void main(String[] args) { // create an empty array list with an initial capacity ArrayList<Integer> arrlist = new ArrayList<Integer>(8); // use add() method to add elements in the list arrlist.add(20); arrlist.add(25); arrlist.add(10); arrlist.add(15); // let us print all the elements available in list for (Integer number : arrlist) { System.out.println("Number = " + number); } // list contains element 10 boolean retval = arrlist.contains(10); if (retval == true) { System.out.println("element 10 is contained in the list"); } else { System.out.println("element 10 is not contained in the list"); } // list does not contain element 30 boolean retval2 = arrlist.contains(30); if (retval2 == true) { System.out.println("element 30 is contained in the list"); } else { System.out.println("element 30 is not contained in the list"); } } } 让我们编译并运行上面的程序,这将产生以下结果 Number = 20 Number = 25 Number = 10 Number = 15 element 10 is contained in the list element 30 is not contained in the list Java.util.ArrayList.clone() Java.util.ArrayList.ensureCapacity()