Java方法傳遞對象引用相當於傳遞指針的值

代碼如下

//dataPage對象包含了List<Statistictime>,此處想改變dataPage裏List裏Statistictime的內容
//將job_state字段從code如yjs轉換爲name如"已結束"
GroupJobService groupJobService = new GroupJobService();
//獲取code與name的映射如key="yjs",value="已結束"
Map<String, String> typeMapping = groupJobService.getTypeMapping();
List<Statistictime> list = dataPage.getList();
String jobState = null;
for (Statistictime statistictime : list) {
    jobState = statistictime.getStr("job_state");
    jobState = jobState!=null&&!"".equals(jobState.trim()) ? jobState.trim() : null;
    if(jobState!=null && typeMapping.containsKey(jobState)) {//typeMapping包含該key
        statistictime.set("job_state", typeMapping.get(jobState));
        statistictime.set("JOB_STATE", typeMapping.get(jobState));
    }
    jobState = null;
}

從上面代碼可以看出,我們只是直接從dataPage獲取相應的List,並作出數據處理後並沒有將List放回dataPage裏,但dataPage的內容已經改變了,以下的簡單demo可以驗證

public class MyTest {
    @Test
    public void testIt() {
        A a = new A();
        a.setA(10);
        System.out.println(a.getA());
        go(a);
        System.out.println(a.getA());
    }
    public void go(A a) {
        a.setA(5);
    }
}
public class A{
    private int a;
    public void setA(int a){
        this.a=a;
    }
    public int getA(){
        return this.a;
    }
}

上面的代碼的運行結果爲:10,5
從而驗證了傳遞引用相當於傳遞指針的值,該值是對象在堆內存裏的地址.