在 Java 中创建默认构造函数
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Create a default constructor in Java
提问by Pieter
I need to create a method with a default constructor, which sets nameto an empty string and sets both creditsand contactHoursto zero. How to do it? Thanks, Pieter.
我需要创建一个默认的构造，其中规定的方法name为空字符串，并将两路credits和contactHours为零。怎么做？谢谢，彼得。
回答by Jon Skeet
Methods don't have constructors... classes do. For example:
方法没有构造函数……类有。例如：
public class Dummy
{
private int credits;
private int contactHours;
private String name;
public Dummy()
{
name = "";
credits = 0;
contactHours = 0;
}
// More stuff here, e.g. property accessors
}
You don't really haveto set creditsor contactHours, as the inttype defaults to 0 for fields anyway.
您实际上不必设置creditsor contactHours，因为int无论如何字段的类型默认为 0 。
You're likely to want at least one constructor which takes initial values - in which case your parameterless one can delegate to that:
您可能需要至少一个采用初始值的构造函数 - 在这种情况下，您的无参数构造函数可以委托给：
public class Dummy
{
private String name;
private int credits;
private int contactHours;
public Dummy()
{
this("", 0, 0);
}
public Dummy(String name, int credits, int contactHours)
{
this.name = name;
this.credits = credits;
this.contactHours = contactHours;
}
// More stuff here, e.g. property accessors
}
回答by oezi
public class Bibabu{
private String name;
private int credits;
private int contactHours;
public Bibabu(){
name = ""; // you could also write this.name and so on...
credits = 0;
contactHours= 0;
}
// more code here
}
回答by Christian Kuetbach
You don't need a constructor:
您不需要构造函数：
public class Dummy
{
private int credits = 0;
private int contactHours=0;
private String name="";
/*
public Dummy()
{
name = "";
credits = 0;
contactHours = 0;
}
*/
// More stuff here, e.g. property accessors
}
回答by user3083485
//constructor
public Account(int id, double balance, Person owner){
this.id = id;
this.balance = balance;
this.owner = owner;
回答by Yel
public class Test {
private String name;
private int credits;
private int contactHours;
public Test {
this( "", 0, 0);
}
public Test (String name, int credits, int contactHours) {
this.name = name;
this.credits = credits;
this.contactHours = contactHours;
}
// more code here
}
