将合并的数据结构来实现一个单一的列表

package com.he.list;

public class Collections {

public static ArrayList union(ArrayList l1, ArrayList l2) {
int l2_length = l2.getLength();
for (int i = 0; i < l2_length; i++) {
if (!l1.contains(l2.get(i))) {
l1.add(l2.get(i));
}

}
return l1;
}

public static void main(String[] args) {
ArrayList l1 = new ArrayList();
ArrayList l2 = new ArrayList();
for (int i = 0; i < 20; i++) {
if (i < 10) {
l1.add(i);
}
l2.add(i);

}

System.out.println("这是列表1：");
for (int i = 0; i < l1.getLength(); i++) {
System.out.print(l1.get(i) + " ");
}
System.out.println();
System.out.println("这是列表2：");
for (int i = 0; i < l2.getLength(); i++) {
System.out.print(l2.get(i) + " ");
}

l1 = Collections.union(l1, l2);
System.out.println();
System.out.println("合并俩个列表：");
for (int i = 0; i < l1.getLength(); i++) {
System.out.print(l1.get(i) + " ");
}
}
}