如何从ArrayList中删除特定的bean对象？
如何从ArrayList中删除特定的bean对象？
提问于 2014-07-05 19:58:18
我想从ArrayList中删除特定的bean对象。我使用 remove 和removeAll方法从ArrayList中删除对象元素，而不是删除元素。
例如，假设下面的代码，
ArrayList<SystemDetailData> systemDetails = new ArrayList<SystemDetailData>();
SystemDetailData data = new SystemDetailData();
data.setId("1");
data.setName("abc");
data.setHost("192.168.1.2");
systemDetails.add(data);
data = new SystemDetailData();
data.setId("2");
data.setName("asd");
data.setHost("192.168.1.45");
systemDetails.add(data);
System.out.println("Before remove : " + systemDetails);
ArrayList<SystemDetailData> systemDetail = new ArrayList<SystemDetailData>();
SystemDetailData data = new SystemDetailData();
data.setId("1");
data.setName("abc");
data.setHost("192.168.1.2");
systemDetail.add(data);
System.out.println("Old data :" + systemDetail);
//Remove object from arraylist - method1
systemDetails.removeAll(systemDetail);
//Remove object from arraylist - method2
systemDetails.removeAll(systemDetail.getId());
systemDetails.removeAll(systemDetail.getName());
systemDetails.removeAll(systemDetail.getHost());
System.out.println("After remove : "+systemDetails);豆类：
public class SystemDetailData extends BusinessData {
/**
*
*/
private static final long serialVersionUID = 1L;
private static final String DOMAIN_NAME = "domainName";
private static final String HOST_NAME = "hostName";
private static final String USER_NAME = "userName";
private static final String PASSWORD = "password";
private static final String INDEX = "index";
private BigInteger index;
private String domainName;
private String hostName;
private String userName;
private String password;
public BigInteger getIndex() {
return (BigInteger) get (INDEX);
}
public void setIndex(BigInteger index) {
set (INDEX, index);
this.index = index;
}
public String getDomainName() {
return (String) get(DOMAIN_NAME).toString();
}
public void setDomainName(String domainName) {
set (DOMAIN_NAME, domainName);
this.domainName = domainName;
}
public String getHostName() {
return (String) get (HOST_NAME);
}
public void setHostName(String hostName) {
set (HOST_NAME, hostName);
this.hostName = hostName;
}
public String getUserName() {
return (String) get (USER_NAME);
}
public void setUserName(String userName) {
set (USER_NAME, userName);
this.userName = userName;
}
public String getPassword() {
return (String) get (PASSWORD);
}
public void setPassword(String password) {
set (PASSWORD, password);
this.password = password;
}
@Override
public String toString() {
return "SystemDetailData [index=" + index + ", domainName="
+ domainName + ", hostName=" + hostName + ", userName="
+ userName + ", password=" + password + "]";
}
@Override
public String getKeyValue() {
String value = "";
if (index != null) {
value = value + "INDEX =" + index + ";";
}
if (domainName != null) {
value = value + "DOMAIN_NAME =" + domainName + ";";
}
if (userName != null) {
value = value + "USER_NAME =" + userName + ";";
}
if (hostName != null) {
value = value + "HOST_NAME =" + hostName + ";";
}
if (password != null) {
value = value + "PASSWORD =" + password + ";";
}
return value;
}
}我的产出低于：
Before remove : [SystemDetailData [index=1, Name=abc, host=192.168.1.2], SystemDetailData [index=2, Name=asd, host=192.168.1.45]]
Old data : [SystemDetailData [index=1, Name=abc, host=192.168.1.2]]
After remove : [SystemDetailData [index=1, Name=abc, host=192.168.1.2], SystemDetailData [index=2, Name=asd, host=192.168.1.45]]我希望产出低于：
After remove : [SystemDetailData [index=2, Name=asd, host=192.168.1.45]]回答 2
Stack Overflow用户
发布于 2014-07-05 20:04:04
如果SystemDetailData类必须实现哈希代码和等于方法。若要扩展我的答案，请在java中从集合中删除对象。Java检查要删除的对象是否在此集合中(如果collection包含与我们要删除的对象相等的对象)。它使用相等的方法。因此，我们必须告诉Java什么是相同的对象:它可以具有相同的名称、相同的id或其他属性(属性)。这就是为什么我们必须实现相等(和hashcode)的原因。
Stack Overflow用户
发布于 2014-07-05 20:56:57
您的SystemDetailData类需要实现一个等于方法。当您在ArrayList上调用remove时，代码正在执行如下操作：
ArrayList<SystemDetailData> items;
void remove(SystemDetailData itemToRemove) {
for ( int i = 0; i < items.size() ++i ) {
if ( items.get(i).equals(itemToRemove) ) {
items.remove(i);
break;
}
}
}他是这样的，除非equals方法对要传递给remove方法的项和集合中的一个项返回true，否则不会删除任何内容。
您需要确切地决定equals方法应该是什么样子，但是，如果两个项目相同，如果ids相同，那么只需向SystemDetailData添加一个方法，例如：
public boolean equals(Object other) {
SystemDetailData otherData = (SystemDetailData)other;
return otherData.getId() == this.getId();
}显然，您需要添加对null、其他类型等的检查，但这会让您了解该方法需要什么样的外观。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/24590098
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