arraylistotherdemo.java

JAVA编程思想源代码 值得一下 很难找的

package chapter9;

import java.util.ArrayList;
import java.util.Iterator;

public class ArrayListOtherDemo {

	public static void main(String[] args) {
		ArrayList<String> col = new ArrayList<String>();
		for (int i = 0; i < 5; i++) {
			col.add(String.valueOf(i));
		}

		System.out.println("开始时 col中的元素有：");
		for (int i = 0; i < col.size(); i++)
			System.out.println("element at " + i + " is " + col.get(i));
		// 判断是否包含一个元素
		String s = new String("4");
		System.out.println("the element 4 is in col is " + col.contains(s));
		// 确保col的大小

		System.out.println("col.size before = " + col.size());
		ArrayList<String> arrl = new ArrayList<String>(10);
		for (int i = 0; i < 3; i++) {
			arrl.add(0, "one");
			arrl.add(1, "two");
		}
		col.ensureCapacity(11);
		col.addAll(arrl);
		System.out.println("col.size after = " + col.size());
		// 输出新的col的所有元素
		String element;
		for (Iterator<String> iter = col.iterator(); iter.hasNext();) {
			element = iter.next();
			System.out.println("element is " + element);
		}

		// 将其赋值给一个数组
		// String[] arr=(String [])col.toArray();
		String[] arr = new String[col.size()];
		arr = (String[]) col.toArray(arr);
		for (int i = 0; i < arr.length; i++) {
			System.out.println("the element at " + i + " is " + arr[i]);
		}

		// 判断col是否为空
		System.out.println("before col is empty is " + col.isEmpty());
		col.clear();
		System.out.println("after col is empty is " + col.isEmpty());

	}

}