Java - 对象引用的初始化方式

Java对象引用的初始化方式:
(1) 在定义对象的位置;
(2) 在类的构造器中;
(3) 在使用对象之前, 即惰性初始化;
(4) 实例初始化.

代码

/**
 * 四种初始化方式
 * <p/>
 * Created by wang on 15/8/5.
 */
class Soap {
    public Soap() {
        System.out.println("Soap");
    }

    @Override
    public String toString() {
        return "Constructed";
    }
}

public class TestInit {
    private String s1 = "Happy"; // 定义初始化
    private Soap s2;
    private String s3, s4;

    // 实例初始化
    {
        s2 = new Soap();
    }

    public TestInit() {
        s3 = "Good"; // 构造器初始化
    }

    @Override
    public String toString() {
        s4 = "Girl"; // 惰性初始化
        return "TestInit{" + "s1=‘" + s1 + ", s2=" + s2 +
                ", s3=‘" + s3 + ", s4=‘" + s4 + ‘}‘;
    }

    public static void main(String[] args) {
        TestInit ti = new TestInit();
        System.out.println(ti);
    }
}
/*
    Output:
    Soap
    TestInit{s1=‘Happy, s2=Constructed, s3=‘Good, s4=‘Girl}
 */