List 中的boolean removeAll(Collection<?> c)是从当前列表中移除指定 collection 中包含的其所有元素。问题是它是如何判断这两个集合中的对象是否是相同?的
[b]问题补充:[/b]
我写了equals,难道我的equals方法有问题?还是不管用啊,我这样写的
[code="java"]package com.sysexpert.util;
import java.util.ArrayList;
import java.util.List;
public class Test extends Thread {
public static void main(String[] args) throws Exception {
test();
}
public static void test( ) {
List a1 = new ArrayList();
for (int i = 0; i < 5; i++) {
SysDB sdb = new SysDB(i, "ip" + i, "name" + i);
a1.add(sdb);
}
List b2 = new ArrayList();
for (int i = 0; i < 7; i++) {
SysDB sdb = new SysDB(i, "ip" + i, "name" + i);
b2.add(sdb);
}
System.out.println("输出集合a1中所有数据的ip:");
for (int i = 0; i < a1.size(); i++) {
SysDB sd = (SysDB) a1.get(i);
System.out.print(sd.getIp()+"\t");
}
System.out.println("\n输出集合b2中所有数据的ip:");
for (int i = 0; i < b2.size(); i++) {
SysDB sd = (SysDB) b2.get(i);
System.out.print(sd.getIp()+"\t");
}
b2.removeAll(a1);
System.out.println("\n集合b2removeAll(a1)后输出所有剩余内容的ip,理论上这里应该只输出ip5 ip6吧:");
for (int i = 0; i < b2.size(); i++) {
SysDB sd = (SysDB) b2.get(i);
System.out.print(sd.getIp()+"\t");
}
}
}
class SysDB {
@Override
public boolean equals(Object obj) {
SysDB sd =(SysDB) obj;
if(sd.id==this.id&&sd.ip==this.ip&&this.name==sd.name){
return true;
}
return false;
}
private long id;
private String ip;
private String name;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getIp() {
return ip;
}
public void setIp(String ip) {
this.ip = ip;
}
public SysDB() {
super();
}
public SysDB(long id, String ip, String name) {
super();
this.id = id;
this.ip = ip;
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}[/code]
这是输出结果:
输出集合a1中所有数据的ip:
ip0 ip1 ip2 ip3 ip4
输出集合b2中所有数据的ip:
ip0 ip1 ip2 ip3 ip4 ip5 ip6
集合b2removeAll(a1)后输出所有剩余内容的ip,理论上这里应该只输出ip5 ip6吧:
ip0 ip1 ip2 ip3 ip4 ip5 ip6