7道Java笔试题

public class TestString { 

    public static void link(String a){ 
         a+="World"; 
    } 
    public static void main(String []args){ 
         String a = "Hello"; 
         link(a); 
         System.out.println(a); 
    } 
} 

System.out.println("ja"+"va" == "java");

final String str = "java";

System.out.println(str=="java")

public class Parent { 
    //1 
    static int a = 1; 
    //2 
    static  
    { 
       a=10; 
       System.out.println("parent static code"); 
    } 
    //4 
    public Parent(){ 
      System.out.println("Parent constructor"); 
      System.out.println("Parent a ="+a); 
    } 
    public static void main(String []args){ 
      System.out.println("*****************"); 
      Parent c = new Child(); 
    }  
} 

public class Child extends Parent{ 
  
    static int a = 2; 
    //3 
    static { 
      a=20; 
      System.out.println("child static code"); 
    } 
    public Child(){ 
      System.out.println("Child constructor"); 
      System.out.println("Child var a="+a); 
    } 
}

public class OuterClass { 

    static int a; 
    int b; 
    private class InnerClass{ 
     public InnerClass(){ 
      System.out.println("InnerClass create:"+a); 
     } 
  } 
    public OuterClass(){ 
       InnerClass ic = new InnerClass(); 
       System.out.println("OuterClass create"); 
    } 
    public static void main(String []args){ 
        OuterClass oc = new OuterClass(); 
    } 
}

public class TestFloat { 
  
    public static void main(String []args){ 
    Float a = new Float(3.4); 
    System.out.println(a.SIZE); 
    a = new Float(34000); 
    System.out.println(a.SIZE); 
    } 
}

public static final int SIZE The number of bits used to represent a float value.

public class Test2
{
    public static void main(String[] args)
    {
        float a = 3.4;
    }

}

float a = (float)3.4;

public class Test2
{
    public static void main(String[] args)
    {
        Float a = new Float(3.4);
        
    }

}

public Float(double value) {
    this.value = (float)value;
    }

a: Stirng a ="Gone With Wind"; 
String t= "Wind"; 
String m; 
m=a-t; 
B: Stirng a ="Gone With Wind"; 
String m ; 
m=a[3]+"one"; 
C: Stirng a ="Gone With Wind"; 
Sting m; 
m=a.toUpperCase(); 
D: 不记得了 

public class A { 
   //3 
    public A(){ 
       a1(); 
    } 
    public void a1(){ 
      System.out.println("A-a1"); 
    } 
} 

public class B extends A{ 

    int bb = 0; 
    //2 
    public B(){ 
    //5 
  bb=1000; 
    } 
    //4 
    public void a1(){ 
  System.out.println("bb is"+bb); 
  System.out.println("B-a1"); 
    } 
    public static void main(String []args){ 
  new B(); 
    } 
}