Java 基础知识

Java基本数据类型

八种基本类型

• 六种数字类型（四个整数型，两个浮点型）：

• 字节型byte 8位
• 短整型short 16位
• 整型int 32位
• 长整型long 64位
• 单精度float 32位
• 双精度double 64位

• 一种字符类型：

• 字符型char 8位

• 一种布尔型：

• 布尔型：boolean 8位，可存储"True"和"false"

Integer是int的封装，跟int的表示范围一样

引用数据类型

包括：类、接口、数组

Java中各种数据的默认值

8种基本类型的初始值：

• byte:0
• short:0
• int:0
• long:0
• float:0.0
• double:0.0
• char: （一个空格）
• boolean:false
• 引用数据类型：
• String:null
• a[0]:0
• cha[0]: （一个空格）

附代码

//////TestMain.java::::
package com.main;
import com.bean.Test;
public class TestMain {
    public static void main(String[] args) {
        Test stu1=new Test();
        System.out.println("8种基本类型的初始值：");
        System.out.println("byte:"+stu1.getBytes());
        System.out.println("short:"+stu1.getShorts());
        System.out.println("int:"+stu1.getInts());
        System.out.println("long:"+stu1.getLongs());
        System.out.println("float:"+stu1.getFloats());
        System.out.println("double:"+stu1.getDoubles());
        System.out.println("char:"+stu1.getChars());
        System.out.println("boolean:"+stu1.isBooleans());
        System.out.println("引用数据类型：");
        System.out.println("String:"+stu1.getStr());
        int[] aa=stu1.getA();
        System.out.println("a[0]:"+aa[0]);
        char[] cha=stu1.getCha();
        System.out.println("cha[0]:"+cha[0]);
    }
}
//////Test.java:::::
package com.bean;
public class Test {
    //8种基本数据类型
    private byte bytes;
    private short shorts;
    private int ints;
    private long longs;
    private float floats;
    private double doubles;
    private char chars;
    private boolean booleans;
    public byte getBytes() {
        return bytes;
    }
    public void setBytes(byte bytes) {
        this.bytes = bytes;
    }
    public short getShorts() {
        return shorts;
    }
    public void setShorts(short shorts) {
        this.shorts = shorts;
    }
    public int getInts() {
        return ints;
    }
    public void setInts(int ints) {
        this.ints = ints;
    }
    public long getLongs() {
        return longs;
    }
    public void setLongs(long longs) {
        this.longs = longs;
    }
    public float getFloats() {
        return floats;
    }
    public void setFloats(float floats) {
        this.floats = floats;
    }
    public double getDoubles() {
        return doubles;
    }
    public void setDoubles(double doubles) {
        this.doubles = doubles;
    }
    public char getChars() {
        return chars;
    }
    public void setChars(char chars) {
        this.chars = chars;
    }
    public boolean isBooleans() {
        return booleans;
    }
    public void setBooleans(boolean booleans) {
        this.booleans = booleans;
    }
    //引用数据类型
    private String str;
    private int[] a=new int[4];
    private char[] cha=new char[4];
    public char[] getCha() {
        return cha;
    }
    public void setCha(char[] cha) {
        this.cha = cha;
    }
    public int[] getA() {
        return a;
    }
    public void setA(int[] a) {
        this.a = a;
    }
    public String getStr() {
        return str;
    }
    public void setStr(String str) {
        this.str = str;
    }
}
source repo / download raw