public class Person {
private Man man = new Man();
public void setMan(Man man) {
this.man = man;
}
public Man getMan() {
return man;
}
}
public class Person {
private Man man = null;
public void setMan(Man man) {
this.man = man;
}
public Man getMan() {
if(this.man = null) {
this.man = new Man();
}
return man;
}
}
private Man man = new Man();
public void setMan(Man man) {
this.man = man;
}
public Man getMan() {
return man;
}
}
public class Person {
private Man man = null;
public void setMan(Man man) {
this.man = man;
}
public Man getMan() {
if(this.man = null) {
this.man = new Man();
}
return man;
}
}
如果这个属性不会直接被外部设置,只是用去其他API接口的时候,可以在声明的时候创建。比如说ArrayList, 他私有了一个array, 如果用默认的构造函数,就需要在内部创建这个array