Java-thinking in Java Chapter 5th exercises

1

//: Main.java/** * String初始化 */class Test {    String s;}class Main {    publicstaticvoidmain(String[] args) {        new Test();        System.out.println("s = " + t.s);    }}/** * Output: s = null *///:~

2

The initialization effect is the same, the member variable definition is determined when the definition is initialized, and is determined when the constructor is constructed.

//: Main.java/** * 初始化 */class Test {    String s1;    "haha";    String s3;    Test () {        "hehe";    }}class Main {    publicstaticvoidmain(String[] args) {        new Test();        System.out.println("s1 = " + t.s1);        System.out.println("s2 = " + t.s2);        System.out.println("s3 = " + t.s3);    }}/** * Output: s1 = null s2 = haha s3 = hehe *///:~

3

//: Main.java/** * 默认构造器 */class Test {    Test () {        System.out.println("This is Test");    }}class Main {    publicstaticvoidmain(String[] args) {        new Test();    }}/** * Output: This is Test *///:~

4

//: Main.java/** * 默认构造器 */class Test {    Test () {        System.out.println("This is Test");    }    Test (String s) {        System.out.println("Test : " + s);    }}class Main {    publicstaticvoidmain(String[] args) {        new Test("Hello");    }}/** * Output: Test : Hello *///:~

5

//: Main.java/** * Constructor Reload * /Class Dog {dog () {System.out.println ("wang! wang! wang! "); } Dog (String s) {System.out.println ("barking!"); } Dog (inti) {System.out.println ("howling!"); }}class Main { Public Static void Main(string[] args) {Dog D1 =NewDog (); Dog D2 =NewDog ("Hello"); Dog D3 =NewDog (1); }}/** * output:wang! wang! wang! barking! howling! *///:~

6

//: Main.java/** * Constructor Overloading-parameter order is different */Class Dog {dog () {System.out.println ("wang! wang! wang! "); } Dog (String s,inti) {System.out.println ("barking!"); } Dog (intI, String s) {System.out.println ("howling!"); }}class Main { Public Static void Main(string[] args) {Dog D1 =NewDog (); Dog D2 =NewDog ("Hello",1); Dog D3 =NewDog (1,"Hello"); }}/** * output:wang! wang! wang! barking! howling! *///:~

7

//: Main.java/** * 默认构造器 */class Test {    "Hello World";}class Main {    publicstaticvoidmain(String[] args) {        new Test();        System.out.println(t.s);    }}/** * Output: Hello World *///:~

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Java-thinking in Java Chapter 5th exercises