JAVA基础笔记1-基本句法

package helloworldapp;
import java.util.*;
public class language_basics {
    /** Variables */
    int speed = 0; //local variable
    static  int numGers = 6; //global int
    final static int pp = 3; //global not changeable variable int
    // primitive data types
    byte gear = 1;
    int g1 = 1;
    short g2 = 1;
    long g3 = 1;
    float g4 = 1;
    double g5 = 1;
    boolean g6 = false;
    char g7 = 'o';
    String g8 = "helloworld";
    // integer literals
    int decVal = 26;//decimal
    int hexVal = 0x1a;//hexadecimal
    int binVal = 0b11010;//binary
    // floating point literals
    double d1 = 123.4;
    double d2 = 1.234e2;
    float f1 = 123.4f;

    /** Arrays */
    int[] anArray = new int[10]; // declare a non-size array and allocate memory for 10 integers
    int[] newArray = {100, 200, 300,
            400, 500, 600,
            700, 800, 900, 1000};
    String[][] names = {
            {"Mr. ", "Mrs. ", "Ms. "},
            {"Smith", "Jones"}
    };
    int a1 = newArray[1];
    char[] copyForm = { 'd', 'e', 'c', 'a', 'f', 'f', 'e',
            'i', 'n', 'a', 't', 'e', 'd'};

    /** Arrays method */
    public int copyArray(){
        char[] copyTo = Arrays.copyOfRange(copyForm,2,9);
        System.out.println(new String(copyTo));
        return 1;
    }
    public void getIdx(){
        int idx = Arrays.binarySearch(copyForm,'a');
        System.out.println(idx);
    }
    public boolean equalArray(){
        return Arrays.equals(copyForm,new char[]{'a'});
    }
    public void putVal(){
        Arrays.fill(copyForm,0,2,'a');
    }
    public void sortArray(){
        Arrays.parallelSort(copyForm);
    }

    /** Operators */
    int result = 1+2;
    // basic arithmetic operators
    private void calc(){
        result -= 1;
        result--;
        result++; // evaluate origin value
        ++result; // evaluate the plus 1 value
        result *= 2;
        result /= 2;
        result %= 2;
        String a = "hellow" + "orld";
        boolean e = !true;
    }
    // condition operators
    private void condition(){
        int v1 = 1;
        int v2 = 2;
        if (v1 == v2)
            System.out.println(v1);
        if (v1!=v2)
            System.out.println(v1);
        if ((v1==2) && (v2==1))
            System.out.println(v1);
        if ((v1==2) || (v2==1))
            System.out.println(v1);
        int res = v1==v2?v1:v2; //condition assignment
    }
    // type comparison: instanceof
    class Parent{}
    interface MyInterface{}
    class Child extends Parent implements MyInterface{}

    private void typeCompare(){
        Parent obj1 = new Parent();
        Parent obj2 = new Child();
        System.out.println("obj1 instanceof Parent: "
                + (obj1 instanceof Parent)); //true
        System.out.println("obj1 instanceof Child: "
                + (obj1 instanceof Child)); //false
        System.out.println("obj1 instanceof MyInterface: "
                + (obj1 instanceof MyInterface)); //false
        System.out.println("obj2 instanceof Parent: "
                + (obj2 instanceof Parent)); //true
        System.out.println("obj2 instanceof Child: "
                + (obj2 instanceof Child)); //true
        System.out.println("obj2 instanceof MyInterface: "
                + (obj2 instanceof MyInterface)); //true
    }

    /** control flow */
    void ifelse(){
        int i = 76;
        String score;
        if (i >= 73){
            score = "good";
        }
        else if (i >= 80){
            score = "very good";
        }
        else {
            score = "excellent";
        }
    }
    void switchcase(){
        int month = 8;
        String monthString;
        switch (month) {
            case 1:  monthString = "January";
                break;
            case 2:  monthString = "February";
                break;
            case 3:  monthString = "March";
                break;
            case 4:  monthString = "April";
                break;
            case 5:  monthString = "May";
                break;
            case 6:  monthString = "June";
                break;
            case 7:  monthString = "July";
                break;
            case 8:  monthString = "August";
                break;
            case 9:  monthString = "September";
                break;
            case 10: monthString = "October";
                break;
            case 11: monthString = "November";
                break;
            case 12: monthString = "December";
                break;
            default: monthString = "Invalid month";
                break;
        }
    }

    void dowhile(){
        int i = 3;
        while (i>0){
            i--;
            return; // exit the method completely
        }
        do{i--;}while(i>0);
    }

    void forloop(){
        for(int i=1; i<11; i++){
            System.out.println("Count is: " + i);
            continue;

        }
        int[] numbers =
                {1,2,3,4,5,6,7,8,9,10};
        for (int item : numbers) {
            System.out.println("Count is: " + item);
            break; // unlabeled break --> another is labeled break(need label outside loop)
        }
    }


}